THE 

REDUCER'S  MANUAL, 

AND 

Being  a  complete,  practical  Hand-Book  on  the  saving  and  reduction 
•        of  every  class  of 

PHOTOGRAPHIC  WASTES, 

AND 

GOLD  AND  SILVER  RESIDUES. 

Comprising  all  the  Wet  and  Dry  Processes  of  Reduction  at  present  known,  with 
many  important  original  Designs,  Formulas  and  Additions. 

BY 

VICTOR  G.  BLOEDE, 

Late  Assistant   Chemist  at  the   Cooper  Institute, 


NEW  YORK : 

JOSEPH    H.  LADD,  PUBLISHER,   No.   91    WHITE  STREET. 
LONDON:  TRUBNER  &  CO. 


4^ 


Entered,  according  to  Act  of  Congress,  in  the  year  1867, 
BY  JOSEPH  H.  LADD, 
In  the  Clerk's  Office  of  the  District  Court  of  the  United  States  for  the 
Southern  District  of  New  York. 


DEDICATED 

TO 

PEOF.   CHAELES   S.  STONE, 

OF  NEW  YORK, 
AS  A  SLIGHT  TOKEN  OP  THE  ESTEEM  OF 

THE  AUTHOR. 


CONTENTS. 


CHAPTER  I. 

History  and  Chemical  Properties  of  nhe  Precious  Metals— 
—Eecipe— Alloys  of  Gold— Salts  of  Gold— Silver — 
Alloys  of  Silver— Salts  of  Silver, .        .        .  .15 

CHAPTER  II. 

The  Furnace  and  the  Management  of  Heat— Selection  ^nd 
Preparation  of  Fuel — Crucibles  and  Melting  Pot,       .  39 

CHAPTER  III. 

On  the  Best  Methods  and  Apparatus  for  Saving  the 
Various  Wastes  Occurring  in  Photography — The 
Bath — The  Sensitized  Plate — Developer  Residues — 
The  Fixing  Solution — Old  Negatives,  Ambrotypes, 
etc.,  etc — Paper  Clippings,  etc.,  etc— The  Print  Wash- 
ings—The Toning  Solution— The  Print  Fixing  Solu- 
tion— The  Apparatus,      .         .         .         .  .39 

CHAPTER  lY. 


Treatment  of  the  Various  Wastes  Preparatory  to  Smelting 
—Burning  Paper  Wastes— Treatment  of  Developer 
Washings— Old  Collodion  Films— The  Hyposulphite 


X 


CONTENTS. 


Fixing  Baths — Treatment  of  the  Cyanide  Fixing  Solu- 
tion— How  to  Precipitate  the  Toning  Bath — Prepara- 
tion of  the  Nitric  Acid  Plate  Cleaning  Solution — Pre- 
cipitation of  Old  Baths,  Nitrate  of  Silver  Solutions, 
etc.,  etc — General  Remarks  and  Practical  Suggestions 
— Precipitation — Filtration  and  Decantation — Drying — 
Roasting — Evaporation — Precipitating  Splutions — For 
Developer  Washings — For  Hyposulphite  Fixing  Baths 
— For  Toning  Bath — The  Nitric  Acid  Plate  Solution — 
For  Old  Baths,  Nitrate  of  Silver  Solutions,  etc.,         -  46 

CHAPTER  Y. 
Fluxing  and  Fusion — Nitrate  of  Potash— Common  Salt 
(Chloride  of  Sodium) — Black  Flux — Resin — Molasses, 
Soap  and  Sugar — Fluxing — Developer  Washings — Col- 
lodion Film  Ashes— Flux  for  Sulphide  of  Silver— Flux 
for  Roasted  Sulphide  of  Silver — The  Toning  Bath 
Precipitate — How  to  Flux  it — Chloride  of  Silver — Re- 
duction— Refining,  Purification  and  Granulation- 
Practical  Suggestions — Formulas  for  Fluxes,  etc.,  etc — 
For  Ashes — For  Developer  Washings  Prepared  by 
First  Method— For  Old  Collodion  Films,  etc.,  etc— For 
Chloride  of  Silver— For  Toning  Bath  Precipitate — For 
Sulphide  of  Silver,  .         .         .         .  .65 

CHAPTER  VL 
Reductions  by  the  Wet  or  Galvanic  Process— Treatment  of 
Wastes  by  Chemical  Action — Paper  Clippings,  Filters, 
Filtering  Cotton,  etc.,  etc — Treatment  of  Developer 
Drainings— Chloride  of  Silver — How  to  Change  it  into 
Nitrate— To  Change  Iodide  or  Bromide  of  Silver  into 
the  Nitrate — To  Change  the  Print  Washings  into  Ni- 
trate of  Silver— How  to  Treat  the  Toning  Bath  Resi- 
due— Old  Solutions  of  Nitrate  of  Silver,  etc.,  etc — 
Reduction  of  Silver  Compounds  to  the  Metallic  State 
by  Galvanic  Action — Sulphate  of  Silver — Old  Nitrate 
of  Silver  Baths,  Waste  Nitrate  Solutions,  etc — The  Ap- 
paratus,     .        ,        .        .        .        ,  .84 


CONTENTS. 


xi 


CHATER  VII. 

Quantitative  Estimation  of  the  Precious  Metals  Contained 
in  Waste  and  Ashes — Table  of  the  Amount  of  Metallic 
Silver  Contained  in  a  Compound  of  Silver — Practical 
Suggestions,         ......  101 

CHAPTER  YIII. 

Useful  Hints  and  Formulas — To  Make  Pure  Chloride  of 
Gold— To  Make  Auro-Chloride  of  Sodium—Another 
Way  of  Making  Pure  Chloride  of  Gold — To  Make  Pure 
Nitrate  of  Silver  from  the  Oxide — Nitrate  from  the 
Carbonate — Testing  Nitrate  of  Silver  as  to  Purity — 
Weights  and  Measures — Troy  Weight — Avordupois 
Weight — Measures  of  Length — Measures  of  Surface — 
Measures  of  Capacity — Measures  of  Length— Long 
Measure — Square  Measure — Measures  for  Liquids- 
Dry  Measure,        .         .         .         .  .  114  ^ 


PART  IL 


CHAPTER  I. 

Sources  of  Gold,  etc— Method  of  Examining  Auriferous  De- 
posits—Substances often  Mistaken  for  Gold — Charac- 
ters of  Native  Gold — Composition  of  Native  Gold — 
Table  Presenting  the  Composition  of  Native  Gold 
from  various  parts  of  the  World — Siberia  and  Ural — 
— Africa— America— Australia — Europe — Properties  of 
Pure  Gold,  129 


xii 


CONTENTS. 


CHAPTER  II. 

Chemical  Examination  of  Gold  Ores— Sulphate  of  Iron  or 
Green  Vitriol — Protochloride  of  Tin — Oxalic  Acid — 
Tests  for  Gold — Test  for  Metals  Usually  Associated 
with  Gold— Copper — Silver — Tests  for  Silver — Plati- 
num— Tests  for  Platinum — Application  of  the  Re- 
agents,      .         .         .         .         .         .  .146 

CHAPTER  III. 

Quantitative  Estimation  of  Gold  Ores  and  Alloys — Quanti- 
tative Estimation  by  the  Touchstone — Quantitative 
Estimation  by  the  Wet  Method— Analysis,       .        .  158 


INTRODUCTION. 


The  great  rapidity  with  wiiicli  pliotograpliy,  as  a 
business,  has  grown  within  the  past  few  years,  has 
been  naturally  followed  by  the  consumption  of  im- 
mense quantities  of  the  precious  metals  and  their  com- 
pounds. Probably  few  photographers  know  that  but 
a  small  portion  of  the  precious  salts  is  actually  used  in 
the  production  of  the  picture,  and  that  more  than 
three-quarters  of  these  valuable  compounds  still  find 
their  way  to  the  waste-pipe.  Yet  such  is  the  fact.  An 
eminent  French  chemist,  in  a  "  Treatise  on  Silver  and 
its  Compounds,"  has  even  taken  pains  to  show  us  that 
nine-tenths  or  ninety  per  cent,  of  the  silver  used  is  act- 
ually lost,  while  only  one-tenth  or  ten  per  cent,  is  util- 
ized in  the  production  of  the  picture.  Though  these 
figures  may  be  a  little  overdrawn,  still  it  is  a  fact  be- 
yond question  that  thousands  of  dollars  are  annually 
lost,  merely  from  want  of  proper  knowledge  and  atten- 
tion to  this  important  subject.  To  assist  the  practical 
photographer  in  accomplishing  this  utilization  of  the 
precious  compounds  in  the  most  perfect  and  economical 
manner,  has  been  our  chief  object  in  penning  this  work. 
For  such  as  prefer  to  have  their  reductions  performed  by 
outside  parties,  the  seventh  chapter  of  the  Manual  was 
written,  which  gives  them  a  sure  defense  against  fraud 
or  imposition. 

1 


INTRODUCTION. 


I  have  carefully  avoided  all  technical  expressions 
and  theoretical  processes,  but  have  confined  myself  to 
strictly  practical  subjects,  and  feel  confident  that  the 
work  will  richly  repay  the  practical  operator  for  the 
trouble  of  perusal,  and  fill  a  vacancy  upon  his  shelves 
which  he  has  long  and  painfully  felt. 

THE  AUTHOR 

Beooklyn,  N.  Y.,  May,  1867. 


THE 


REDUCER'S  MANUAL- 


CHAPTEE  1. 

HISTORY    AND     CHEMICAL    PROPERTIES     OF    THE  PRECIOUS 
METALS.* 

The  word  element  is  understood  at  the  present  time 
as  indicating  every  substance  which  chemists  have  not 
succeeded  in  decomposing  or  separating  into  different 
component  parts.  All  the  metals  at  present  known, 
both  the  common  and  the  precious  ones,  have  this 
characteristic  and  are  consequently  termed  elements. 
Gold,  silver  and  platinum  are  called  the  noble  metals, 
from  the  fact  that  they  do  not  associate  with  the  com- 
mon elements,  but  prefer  to  shine  alone  in  their  inborn 
glory.  One  of  the  commonest  and  most  widely  dif- 
fused of  the  elements  is  a  constituent  of  the  air  we 
breathe,  and  this  substance  which  is  a  gaseous  body  is 
called  oxygen,  from  the  fact  that  it  imparts  to  many 
of  its  compounds  the  character  of  an  acid.  This  ele- 
ment combines  readily  with  the  common  metals,  trans- 
forming them  into  perfectly  new  and  unrecognizable 
substances.     Compare,  for  instance,  a  clean,  bright 

*  The  substance  of  this  chapter  has  been  freely  drawn  and  condensed 
from  the  work  of  the  celebrated  German  mineralogist,  Francis  von  KobeU. 


16 


THE  KEDUCER's  MANUAL. 


steel  blade  witli  a  badly  rusted  one.  In  the  former  we 
see  a  dazzling  metallic  luster;  and  in  the  latter  a  dull 
red,  or  yellow  friable  earthy  substance  ;  and  the  cause 
of  this  wonderful  change  is  nothing  more  than  the  com- 
bination of  the  iron  or  steel  with  this  gaseous  body, 
oxygen.  Eust  of  a  similar  kind  is  formed  upon  all  the 
common  metals,  while  the  noble  ones  resist  for  ages  this 
enemy  of  their  glory. 

Chemists,  who  have  appropriately  been  called  the 
tyrants  of  the  elements,  may,  it  is  true,  unite  by  force, 
as  it  were,  the  noble  metals  with  oxygen,  nitrogen  or 
hydrogen,  three  gaseous  elements  which  exist  in  air 
and  water;  but  their  union  is  of  short  duration;  the 
slightest  touch  or  blow  is  sufficient  to  cause  a  frightful 
revolution,  and  the  compound  explodes  with  fearful 
violence,  shattering  everything  with  which  it  comes  in 
contact.  These  combinations  are  better  known  under 
the  name  of  the  Fulminates  of  the  noble  metals. 

Gold  and  platinum  resist  the  action  of  almost  every 
solvent  that  can  be  applied,  only  one  substance, 
in  fact,  being  known  that  effects  complete  solution, 
namely,  chlorine,  which  is  most  readily  obtained  for 
this  purpose  by  mixing  one  volume  of  hydrochloric 
acid  with  two  of  nitric.  From  this  property  the  com- 
pound of  these  two  acids  has  received  the  name  of 
aqua  regia,  or  king's-water.  In  consequence  of  their 
great  resistance  to  foreign  influences,  the  noble  metals 
are  generally  found  in  a  pure — that  is,  uncombined — 
or  metallic  condition;  while,  directly,  the  contrary  is 
the  case  with  the  common  metals. 

Penetrating  further  into  the  analysis  of  the  peculi- 
arities of  the  jioble  metals,  the  great  ductility  which 


THE  reducer's  MANUAL. 


17 


characterizes  tlie  ting  of  metals,  gold,  beyond  any 
other  known  substance,  deserves  our  especial  atten- 
tion. 

It  is  the  glory  of  the  sun  that  it  possesses  the  power 
to  spread  and  unfold  its  rays  so  widely,  that  it  illu- 
mines not  only  the  gorgeous  palace  of  the"  sovereign, 
but  also  shines  with  a  friendly  light  into  the  poor 
man's  hovel,  or  silently  creeps  through  the  narrow 
chinks  and  crevices  of  the  dreary  dungeon.  This  com- 
parison seems  almost  exaggerated,  but  the  extraor- 
dinary ductility  of  gold  admits  of  a  diffusion  which  al- 
lows even  the  poorest  to  rejoice  in  its  bright  luster 
and  sunny  color.  There  are,  doubtless,  thousands  who 
have  never  seen  a  ruby  or  sapphire,  but  none  who  do 
not  know  what  gold  looks  like.  When  we  reflect  upon 
its  wide  diffusion  in  gilding  and  painting  on  innumer- 
able familiar  objects  ;  on  rings,  pins,  thimbles  ;  on 
chains  and  watches,  cups  and  vases,  and  thousands  of 
articles  of  crockery-ware,  we  at  once  see  that  it  has 
long  been  the  common  property  of  the  world.  Every- 
one knows  the  saying,  that  "  a  horse  and  its  rider  may 
be  gilt  with  a  ducat,"  but  the  divisibility  of  gold  is  far 
greater  than  this.  A  single  grain  of  gold,  not  larger 
than  the  head  of  a  very  small  pin,  may  be  drawn  out 
into  five  hundred  feet  of  wire.  Yet  even  this  is  not  its 
utmost  Umit.  If  silvered  wire  is  gilt  and  then  rolled, 
a  film  of  gold  is  produced  not  one  twelve-millionth  part 
of  an  inch  in  thickness. 

The  extraordinary  ductility  of  gold  was  already 
known  to  the  ancients,  and,  as  Pliny  relates,  they  were 
acquainted  with  the  art  of  beating  it  and  gilding  on 
^tone. 


18 


THE  KEDUCER's  MANUAL. 


Silver  is  also  exceedingly  ductile,  thougli  not  to  such 
an  extent  as  gold;  platinum  is  inferior  to  silver. 

The  noble  metals  are  likewise  distinguished  by  being 
much  heavier  than  the  common  ones,  gold  and  pla- 
tinum being  more  than  nineteen  times  heavier  than 
water,  bulk^or  bulk. 

The  great  weight  of  gold  is  turned  to  particular  ad- 
vantage in  mining;  clay  and  sand  being  hardly  three 
times  heavier  than  water,  may  be  washed  off,  while  the 
gold  sinks  to  the  bottom. 

This  is  the  basis  of  the  process  known  as  "panning." 

The  noble  metals,  moreover,  are  not  volatile,  and, 
generally  speakmg,  unalterable  by  exposure  to  heat, 
while  the  common  metals  are  all  volatilized  at  high 
temperatures,  or,  if  the  air  has  access,  combine  with  its 
oxygen.  Taking  all  these  characteristics  together,  we 
perceive  at  once  that  the  noble  or  precious  metals  are 
gifted  with  pre-eminence  in  many  respects,  and  while 
very  generally  distributed,  they  never  run  in  large 
quantities,  they  have  in  this  way  acquired  a  still  more 
exalted  value. 

When  we  ask  as  to  the  antiquity  of  these  nobihties, 
gold  and  silver,  at  least,  shine  in  this  respect;  for  they 
are  the  two  metals  which  have  been  longest  known  to 
man.  A  piece  of  gold  and  silver,  in  the  pure  state  in 
which  it  always  occurs,  could  not  have  remained  long 
undiscovered,  and  its  malleabihty  and  ductihty  would 
have  insured  its  application  to  many  useful  purposes. 

Silver  is  also  of  the  highest  antiquity,  and  a  weighed 
quantity  of  the  same  was  used  as  a  trading  medium 
already  in  the  time  of  Abraham,  and  both  metals  are 
frequently  mentioned  in  the  history  of  the  ancient 


THE  KEDUCER*S  MANUAL. 


19 


Egyptians,  Phoenicians,  Indians,  Chinese  and  Scandi- 
navians mth  the  highest  respect  and  veneration.  The 
ancient  Greeks  made  their  drinking-cups  of  gold.  In 
the  "  Songs  of  Orpheus,"  the  wrestler,  Anchaeus,  wins 
a  golden  drinking-cup ;  Hercules  gains  a  silver  pitcher 
as  a  boxer,  and  Castor  a  golden  horse  for  his  skill  in 
riding,  etc.,  etc.  In  ancient  history  the  metals  are 
frequently  compared  to  the  planets.  Hence,  gold  re- 
ceived the  name  of  the  Sun;  silver,  that  of  the  Moon; 
and,  among  the  comnion  metals,  lead  bore  the  sign  of 
Saturn;  tin,  of  Jupiter;  copper,  of  Venus;  iron,  of  Mars; 
and  quicksilver,  that  of  Mercury,  etc.,  etc.  It  is  a  well- 
known  fact,  however,  that  the  value  of  the  noble  metals 
has  increased  immensely  during  the  past  few  centuries ; 
and  since  the  Seeress  of  Prevorst  has  proved  that,  in  a 
magnetic  condition,  she  had  an  ungovernable  inclina- 
tion for  gold,  "  the  avarice  of  the  miser  who  digs  with 
a  fiendish  pleasure  in  his  heap  of  coin,  is,  to  a  certain 
extent,  justified."  If  the  law  were  not  so  exceedingly 
limited  in  its  views,  and  took  notice  of  such  experi- 
ments as  that  of  the  Seeress,  the  thief  who  stole  a  gold 
snuff-box  would  not  be  punished  by  far  as  severely  as 
he  who  stole  a  brass  one,  and  he  would  soon  learn  to 
explain  that,  at  the  time  of  the  theft,  he  was  in  a  mag- 
netic condition. 

The  great  value  of  gold  and  the  influence  it  has  ever 
possessed  in  governing  the  luxuries  and  creed  of  a 
people,  naturally  stimulated  the  fancy  and  gave  origin 
to  the  endeavors  which  have  been  made  from  the  ear- 
liest antiquity  to  produce  it  artificially.  Alchemy,  as 
a  branch  of  the  history  of  the  precious  metals,  is  of 
such  absorbing  interest,  that  I  have  thought  it  not  out 


20 


THE  reducer's  MANUAL. 


of  the  way  to  devote  a  part  of  the  chapter  to  an  ac- 
count of  this  wonderful  mania.  The  exciting  task  of 
the  followers  of  alchemy  was  to  convert  the  base  metals, 
such  as  lead,  copper  or  tin,  into  gold.  Mystery  and 
miracle  would  naturally  form  part  of  the  means  to  ob- 
tain such  ends,  and  the  imagination  wandered  over  a 
region  which  it  was  unwiUing  to  leave.  Still  we  can- 
not say  that  the  transmutation  of  the  metals  is  an  im- 
possibility; indeed  there  are  many  indications  which 
render  it  highly  probable,  and  many  of  the  most  emi- 
nent chemists,  even  of  the  present  time,  beheve  that 
the  great  dream  of  the  alchemists  will  once  be  realized. 

The  first  traces  of  alchemy,  or  the  hermetic  or  spa- 
giric  art  (from  airacLv,  to  separate,  and  ayapeiv,  to  unite), 
appear  to  be  of  Egyptian  origin ;  and  a  fabulous  Hermes 
Trismegistos  is  said  to  have  founded  it  2000  years  be- 
fore the  birth  of  Christ;  but  it  is  only  from  the  fourth 
century  of  our  era  that  we  begin  to  have  distinct  ac- 
counts of  it. 

The  art  of  gold-making  came  from  the  Egyptians  to 
the  Greeks  and  Alexandrians,  and  subsequently  to  the 
Arabs;  in  the  thirteenth  century  it  had  diffused  itself 
all  over  Spain,  France,  England  and  Germany,  and  in 
1700  it  was  raging  as  a  mania  all  over  the  civilized 
world.  The  most  important  point  in  the  alchemical 
creed  was,  that  there  existed  a  substance  having  the 
power  of  converting  the  base  metals  into  gold  or  silver; 
this  substance  was  called  the  "philosopher's  stone," 
the  "  great  elixir"  or  "  magisterium ;"  it  not  only  had 
the  power  of  this  transmutation,  but  it  possessed  the 
splendid  property  of  making  the  old  young  again  and 
prolonging  life  to  an  indefinite  period.  Thus  Solomon 


THE  KEDUCEb's  MANUAL. 


21 


Trismosin,  in  a  treatise  entitled  "  AurenmVellus/'  (1490) 
tells  us  (oh  joy  !)  that  it  is  an  easy  matter  for  him  to 
keep  himself  alive  by  the  use  of  this  stone,  and  that 
he  intends  to  live  long  enough  to  see    the  last  day."* 

The  process  of  obtaining  the  gold  by  the  use  of  this 
stone  was  very  simple;  the  base  metal  was  only  fused 
and  small  portions  of  the  "  great  elixir were  then 
thrown  upon  it,  when  lo  !  a  lump  of  pure  gold  or  silver, 
as  the  case  might  be,  was  found  in  the  place  of  the 
common  metal. 

The  stone  had  wonderful  power;  one  part  being  suf- 
ficient to  "transmute"  at  least  one  million  (1,000,000) 
parts  of  the  base  metal  into  gold.  But  how  vfas  this 
wonderful  stone  obtained  ?  how  could  it  be  manufac- 
tured? "  Ay,  there's  the  rub The  older  alchemists 
believed  that  supernatural  means  were  required  for  its 
production;  some  believed  that  the  devil  and  other 
lesser  demons  and  gnomes  held  the  secret,  which  could 
only  be  purchased  from  them  at  the  expense  of  the 
soul;  others  believed  the  secret  was  first  made  known 
to  man  by  angels  from  heaven. 

The  alchemists  of  later  times  depended  more  on 
earthly  means  for  producing  it,  and  accordingly 
boiled,  fused  and  distilled  together  the  most  diverse 
and  wonderful  substances  their  feverish  imaginations 
could  conjure  up.  Believing  that  many  of  my  readers 
would  Hke  to  learn  the  most  bewitching  art  of  gold- 
making,  and  as  we  firmly  believe  that  this  grand  result 
can  only  be  accomplished  by  supernatural  means,  we 
give  here  "  a  little  recipe  "  by  which  they  can  conjure 

*  Wliere  is  Solomon  1 

1* 


22 


THE  reducer's  MANUAL. 


up  the  foreman  of  the  devils  (for  consultation  only). 
This  recipe  was  taken  from  an  old  work  entitled  the 
"  Gold-Maker's  Guide." 

RECIPE. 

Take  of  the  gall  of  a  black  tomcat,  killed  when  the 
night  approacheth,  one  part;  of  the  brains  of  a  night 
owl,  taken  from  out  its  bead  when  the  morning  dawn- 
eth,  five  parts;  mix  in  the  hoof  of  an  ass,  when  the 
tide  turneth,  and  leave  it  until  it  doth  breed  maggots; 
place  it  upon  thy  breast-bone  when  the  moon  shineth 
bright — and — thou  wilt  see  a  sight  which  the  eye  of 
mortal  man  ne'er  beheld  afore. 

Reader,  should  you  not  be  successful,  we  can  but 
encourage  you  by  repeating  the  well-known  nursery 
rhyme — 

If  you  don't  at  first  succeed, 
Try,  try  again. 

But  we  must  not  suppose  that  the  alchemist  was  al- 
lowed to  grope  in  the  dark  ;  by  no  means  ;  many 
"  guides  "  to  the  fabrication  of  the  great  stone  were 
published,  but  unfortunately  those  that  were  written 
plainly  never  yielded  an  available  stone,  while  those 
that  were  written  mysteriously  (as  nearly  all  were) 
were,  of  course,  not  understood.  The  titles  of  the 
following  works  already  give  us  an  idea  of  the  contents 
of  such  "  guides."  In  1649  appeared,  "  A  Master-Key 
to  the  Opened  Heart  of  Fatherly  Philosophy,"  and  the 
"  Childbed  of  the  Philosopher's  Stone." 

In  1700,  "  PhilosojDhical  Field  Sports  and  Nymph- 
Catching,"  and  the  Brightly  Shining  Sun  in  the 
Alchemical   Firmament  of  the  German  Horizon." 

Chymical  Moonshine  ;"  (Frankfort,  1744)  the  Chy- 


THE  REDTJCERS  MANUAL. 


23 


mical  King  in  his  Eobe  of  Purple/'  (1725)  etc.,  etc. 
Many  of  these  "  guides "  were  sold  very  cheap,  con- 
sidering the  immense  wealth  they  contained,  few  cost- 
ing more  than  a  few  cents. 

Most  of  these  "  valuable  guides  "  had  very  peculiar 
prefatory  notices,  for  instance,  "  If  thou  be'st  not  alto- 
gether too  stupid,  and  wishest  not  to  climb  too  high, 
this  little  book  will  tell  you  how;"  or,  "Ye  who  do  not 
seek  too  much  but  expecteth  to  find  little,  will  be 
satisfied." 

We  would,  however,  wrong  the  alchemical  writers 
if  we  were  to  attribute  this  mysterious  manner  alto- 
gether to  an  intent  of  deception;  this  was  not  always 
the  case,  it  arose  partly  from  the  belief  that  it  was 
wicked  to  make  public  this  great  secret,  or  that  it  might 
even  cause  the  death  of  the  writer  before  the  pages 
were  completed.  Hence,  Wilhelm  von  Schroeder,  a  dis- 
tinguished chemist  (1G84),  informs  us,  in  a  work  en- 
titled "Necessary  Instructions  in  the  Art  of  Gold-Mak- 
ing," that  when  philosophers  speak  openly,  a  deceit  lies 
behind  their  words;  while  when  they  speak  enigmatic 
colly,  they  may  be  depended  upon. 

This  maxim  seems  to  be  very  generally  understood 
and  practiced  even  by  philosophers  of  the  present  day. 
In  fuU  descriptions  of  gold-making  many  preparatory 
notices  are  mentioned  as  absolutely  indispensable. 
Thus:  Eeader,  prepare  first  a  ^^philosophic  mercury'' 
and  a  ''philosophic  stone  f  these  are  thoroughly  tritu- 
rated together  and  exposed  to  a  very  gentle  heat  in  a 
vessel  of  particular  form;  after  a  certain  time  they 
yield  a  black  mass  which  was  called  "  raven's-head;" 
by  still  continuing  the  heat,  the  substance  becomes 


24 


THE  reducer's  MANUAL. 


gradually  white,  and  is  then  called  the  "white  swan;" 
if  the  heat  be  now  increased,  and  still  continued  for  a 
certain  time,  the  white  mass  becomes  orange  yellow 
and  at  last  bright  red;  the  operation  is  then  completed 
and  the  stone  obtained  in  its  highest  perfection. 

First  of  all,  a  philosophic  quicksilver  was  necessary, 
brit  where  this  wonderful  sabstance  was  to  be  found 
nobody  knew  ;  some  sought  for  it  in  the  common 
metals;  some  in  dew,  rain  and  snow;  others  (as  the 
recipe  given  above  proves)  expected  to  find  it  in  toads, 
snails,  lizzards,  snakes,  owls,  and  plants  and  animals 
of  all  kinds.  As  there  were  so  many  "  guides,"  the 
precious  metals  themselves  could  not  be  lacking.  Thus 
the  Danish  ducats  of  1647  were  made  of  gold,  obtained 
by  artificial  means  by  the  alchemist  of  Christian  IV., 
named  Casper  Harbach.  So,  under  the  Emperor  Fer- 
dinand III.,  1648,  a  large  medal  was  struck  from  gold 
that  had  been  obtained  in  the  emperor's  presence  by 
the  transmutation  of  quicksilver;  this  transmutation 
being  affected  by  means  of  a  dark  red  powder  which 
had  been  presented  to  the  emperor  by  an  unknown 
person.  In  like  manner,  the  ducats  struck  under  Land- 
grave Ernest  Lewis  of  Hesse  Darmstadt,  were  of  arti- 
ficial gold,  produced,  as  was  said,  by  the  transmuta- 
tion of  lead;  and  the  specie  dollars  of  1717  were  of 
such  silver. 

In  the  year  1423,  King  Henry  VI.  of  England  issued 
several  proclamations  encouraging  the  study  of  gold- 
making,  in  order  to  obtain  means  to  pay  the  debt  of 
the  state.  Edward  IV.  of  England,  in  1476,  accorded 
to  a  company  "  a  four  yep-re  privilege  of  making  gold 
from  quicksilver."    The  Elector  Augustus  of  Saxony, 


THE  EEDUCEr's  MANUAL. 


25 


who  lived  about  1560,  was  a  great  follower  of  alchemy, 
and  had  an  extensive  laboratory  of  his  own  which  the 
people  called  "the  gold-house/'  whether  from  the 
amount  made  in  it  or  spent  on  it  does  not  appear. 

Kings,  emperors  and  nobles  (especially  men  who 
had  plenty  of  money  to  spend)  were  always  found  at 
the  head  of  the  most  ardent  alchemical  movements. 
In  these  times  of  wild  turmoil  and  excitement,  in  which 
every  loeasant  had  his  laboratory  for  "  gold-making," 
there  were  still  a  few  who  kept  cool.  Thus  Pope  Leo 
X.  once  received  a  dedication  of  an  enthusiastic  poem, 
by  an  alchemist  named  Augurelli,  in  recognition  of 
which  His  Holiness  returned  an  empty  purse  with  a 
note,  that  the  happy  man  who  was  master  of  such 
pleasing  art,  was  only  in  want  of  a  purse  in  which  to 
store  the  treasure  he  made. 

Although  it  is  true  that  there  are  many  cases  of 
gold-making  in  which  no  deceit  was  discovered,  still 
there  were  many  more  which  were  openly  proved  to 
be  false.  The  fate  of  those  who  were  convicted  of  de- 
ceit, was  to  be  hung  up  in  a  dress  covered  with  tinsel; 
while  those  who  "  produced  "  gold,  in  a  seemingly  mi- 
raculous manner,  often  had  as  bad  or  even  worse  fate; 
they  were  seized,  shut  up,  and  ordered  to  make  gold, 
to  a  certain  amount  daily,  in  default  of  which,  they 
were  beaten  and  kicked  about  in  a  most  horrible  man- 
ner, and,  in  fact,  maltreated  in  every  conceivable  way. 
This  fell  to  the  lot  of  an  unfortunate  little  tailor  of 
Strassburg,  who  by  some  unknown  means  had  obtained 
(from  the  devil  he  thought)  a  small  fragment  of  the 
"  great  magisterium,"  but  w^s  entirely  ignorant  of  its 
composition  or  manufacture. 


26 


THE  reducer's  MANUAL. 


It  would  be  far  beyond  the  limits  of  this  little  book 
to  follow  further  the  most  interesting  mania  which 
raged  for  more  than  one  thousand  years,  to  observe 
how  self-interest,  passion,  stupidity  and  madness  every- 
where followed  in  its  track  until  the  science  of  chem- 
istry grew  stronger  and  stronger,  and  one  by  one 
forced  the  old  superstitious  beliefs  from  the  ground, 
and  made  way  for  new  facts  and  great  truths  in  the 
3cience  of  God's  great  creations. 

Gold  and  silver  are  generally  found  in  the  metalHc 
or  uncombined  condition.  The  form  in  which  native 
gold  occurs  is  rarely  a  regular  one.  It  is  mostly  found 
in  small  granules,  threads,  dust  or  powder,  spangles  or 
laminae. 

It  is  softer  than  copper  and  fusible  without  difficulty. 
The  extraction  of  gold  from  its  ores  is  simply  affected 
by  crushing  the  ore  to  a  fine  powder  and  panning," 
as  above  described,  or  by  amalgamation.  The  process 
known  as  amalgamation,  consists  in  treating  the  pow- 
dered ore  with  mercury,  which  combines  with  the  me- 
tallic substances  forming  an  amalgam  or  "  butter 
this  butter  is  placed  in  bags  of  buckskin  and  subjected 
to  a  strong  pressure,  the  mercury  oozes  through,  and 
a  semi-solid  miass  remains  in  the  bag,  which  is  placed 
in  iron  retorts  and  distilled ;  by  this  process  the 
volatile  mercury  is  driven  off  and  recondensed,  and 
the  gold  or  silver  remains  as  a  hard  cake  in  the 
retort. 

Gold  is  very  generally  diffused  over  the  earth's  sur- 
face, the  largest  quantities  being  found  in  the  United 
States. 

Germany,  Russia,  Australia,  Mexico  and  South 


THE  REDUCEB's  MANUAL. 


27 


America  also  yield  large  quantities  of  gold  and  silver 
annually. 

Gold,  as  it  is  found  in  nature,  is  rarely  without  an 
admixture  of  silver. 

The  preparation  of  gold  known  as  the  purple  of  Cas- 
sius,  or  gold  purple,  consists  simply  of  metallic  gold 
in  a  very  fine  state  of  division,  and  is-  of  great  import- 
ance in  the  coloring  and  painting  of  glass  and  porce- 
lain, imparting  to  it  that  magnificent  purple  color  so 
much  admired.  This  preparation  of  gold  was  first 
described  by  Andreus  Cassius,  in  1685,  after  whom  it 
received  its  name,  and  it  is  formed  most  readily  as  a 
purple  precipitate  when  solutions  of  the  chlorides  of 
gold  and  tin  are  mixed;  but  the  preparation  of  a  good 
article  requires  many  precautions. 

ALLOYS  OF  GOLD. 

Gold  readily  unites  with  other  metals  by  fusion,  but 
its  alloys  with  copper  and  silver  are  alone  of  import- 
ance. These  metals,  when  added  in  fixed  proportions, 
give  gold  a  greater  hardness,  making  it  more  fit  for 
coinage  and  goldsmith's  work. 

The  proportions  of  gold  in  an  alloy  is  expressed  in 
carats.  A  mark  is  divided  into  twenty-four  carats;  and 
if  twenty-four  carats  of  the  gold  alloy,  for  instance, 
contain  ten  parts  of  the  foreign  metal,  it  is  said  to  be 
fourteen  carats  fine;  if  it  contains  two  parts  of  the 
base  metal,  it  is  twenty-two  carats  fine,  etc.,  etc. 

Alloying  with  copper  is  called  red  carating ;  with 
silver^  white  carating. 

SALTS  OF  GOLD. 

There  is  but  one  important  salt  of  gold,  the  percblo- 


28 


THE  reducer's  MANUAL. 


ride,  (AuClg)  consisting  of  one  equivalent  of  gold 
united  to  three  of  chlorine. 

Besides  this,  there  is  the  oxide  of  gold  (AuO),  the 
sulphide  (AuS,  AuSg),  the  protocyanide  (Au,  Cy)  and 
the  percyanide  (Au,  Gj^);  but  these  compounds  are  of 
no  interest  whatever  to  the  photographer. 

SILVER. 

Silver  is  found  native  in  almost  precisely  the  same 
form  as  gold.  It  is  sometimes  found  in  combination 
with  sulphur  in  the  form  of  black  powder — sulphuret 
or  sulphide  of  silver,  known  as  argentite  in  mineral- 
ogy; and  with  chlorine  as  chloride  or  horn  silver — it 
is  sometimes,  though  rarely,  found  in  combination 
with  iodine  as  iodide,  and  with  bromine  as  the  bro- 
mide of  silver.  The  smelting  of  silver  ores  is  also  very 
simple,  and  the  extraction  is  only  connected  with  dif- 
ficulties when  the  silver  ore  is  mingled  in  very  small 
quantities  through  quartz  or  other  rock.  Silver  is 
also  found  very  generally  distributed  over  the  earth, 
the  principal  mines  being  in  Mexico,  Peru  and  other 
South  American  States. 

ALLOYS  OF  SILVER. 

By  the  addition  of  small  portions  of  copper  to  silver 
the  metal  is  rendered  harder  and  more  sonorous,  while 
its  color  is  not  impaired. 

All  silver  coin  contains  a  certain  amount  of  copper 
to  render  it  more  durable.  The  standard  silver  of  this 
country  consists  of  92*5  parts  of  silver  and  7*5  of  cop- 
per. Besides  this,  silver  forms  various  alloys  with  tin, 
lead,  zinc,  etc. ;  but  these  are  of  no  practical  importance. 


THE  BEDUCEr's  MAKTJAL. 


29 


SALTS  OF  SILVER 

The  principal  salts  of  silver  are  the  nitrate  (AgO, 
NO  5),  the  chloride  (Ag,  CI),  the  sulphide  {Ag,  S),  the 
hyposulphite  (AgO,  SgOg,  5H0),  the  cyanide  (Ag,  Cy), 
the  iodide  (Agl)  and  the  bromide  (Ag,  Br);  these  com- 
pounds being  too  well-known  to  every  practical  photo- 
grapher to  require  any  further  description. 


CHAPTEE  11. 

THE  FURNACE  AND  THE  MANAGEMENT  OF  HEAT. 

The  subject,  wliicli  necessarily  is  of  primary  import- 
ance, and  has  the  first  claim  to  our  attention,  is  a  suit- 
able apparatus  or  furnace,  in  which  the  heat,  in  dry 
reductions,  may  be  quickly  and  efficiently  produced. 

The  imperfect  knowledge  of  this  important  subject 
has  been,  as  it  were,  the  great  stumbling-block  of  the 
practical  photographer  in  attempting  the  reduction  of 
his  wastes.  Nevertheless,  it  is  a  matter  of  great  sim- 
plicity. Some  persons  have  an  idea  that  a  furnace  for 
the  reduction  of  gold  and  silver  residues  involves  a 
large  outlay,  much  time  and  scientific  knowledge;  but 
this  is  an  erroneous  impression,  which  we  shall  try  to 
refute  in  the  course  of  this  work.  We  shall,  therefore, 
proceed  to  describe  several  simple  devices,  which  are 
very  efficient  forms  of  apparatus  for  the  smelting  of 
gold  and  silver  residues,  and  which  can  all  be  put  to- 
gether at  the  outlay  of  a  merely  nominal  sum  of  money. 

The  main  parts  of  every  furnace  are,  first,  the  body 
in  which  the  heat  is  generated;  secondly,  the  grate  or 
bars,  upon  which  the  fuel  rests;  thirdly,  the  ash-pan 
for  receiving  the  clinkers  and  residue;  and  fourthly, 
the  smoke-pipe  for  carrying  off  the  gaseous  products 
of  combustion. 

There  are  three  different  furnaces  in  use  for  the  re- 
ducing operations.    The  Wind  Furnace,  in  which  the 


THE  BEDUCEb's  MANUAL. 


31 


draft  of  tlie  chimney  alone  urges  the  fire ;  common 
stoves  belong  to  this  class.  If  properly  built,  and  pro- 
vided with  a  high,  clean  and  unobstructed  chimney, 
they  answer  tolerably  well  for  reducing  operations. 
The  Eeverberatory  Furnace,  in  which  the  flame  of  the 
fire  is  condensed  and  reflected  upon  the  fused  masM  by 
a  funnel-shaped  dome,  which  will  be  more  fully  ex- 
plained under  another  head.  This  furnace  is  best 
adapted  for  the  reduction  of  gold  and  silver  wastes, 
giving  great  intensity  of  heat  with  continuity  of  action; 
and  lastly,  the  Blast  Furnace,  used  to  produce  a  quick 
and  intense  heat.  The  combustion,  in  this  case,  is 
urged  by  a  current  of  air,  forced  through  the  fire  by 
means  of  a  bellows  or  rotating-fan.  This  style  of  fur- 
nace is  used  mostly  in  the  refining  or  granulation  of 
the  precious  metals.  An  ordinary  small  cylinder  stove 
may  be  readily  altered  into  the  three  different  forms 
above  mentioned.  When  used  as  a  wind  furnace,  the 
degree  of  heat  which  can  be  produced  in  it  depends 
upon  the  height  of  the  chimney  into  which  the  flue 
passes,  and,  as  a  general  rule,  the  higher  the  chimney 
the  greater  will  be  the  heat. 

It  is,  therefore,  preferable,  if  possible,  to  have  the 
stove  placed  in  a  cellar,  or,  at  least,  on  the  lower  floor 
of  a  building.  The  intensity  of  the  heat  may  also  be 
vastly  increased,  by  so  proportioning  the  dimensions 
of  the  furnace  and  the  chimney,  that  their  diameters 
are  equal,  and  the  height  of  the  chimney  be,  if  possible, 
fifty  or  sixty  times  the  diameter  of  the  body  of  the 
furnace. 

By  following  these  directions,  a  wind  furnace  of  the 
best  kind  can  be  obtained,  but  it  is  always  preferable 


32 


THE  reducer's  MANUAL. 


to  use  a  reverberatory  or  blast  furnace,  especially  in 
the  reduction  of  paper  ashes  and  sulphide  of  silver; 
the  first  being  difficult  of  fusion  on  account  of  the 
large  amount  of  silicious  and  carbonacious  matter 
which  it  contains;  the  second  being  one  of  the  most 
obstinate  compounds,  in  regard  to  perfect  reduction, 
known  in  metallurgy. 

To  construct  a  furnace  on  the  reverberatory  prin- 
ciple, the  body  should  first  be  lined  with  a  thick 
coating  of  refractory  clay,  that  it  may  more  perfectly 
withstand  the  intense  heat  to  which  it  will  be  sub- 
jected. 

This  done,  the  orifice  on  the  back  of  the  stove, 
intended  to  receive  the  stove-pipe,  should  be  plastered 
up  with  a  thick  lump  of  fire-clay.  A  funnel-shaped 
dome  with  an  opening  at  the  top,  and  large  enough  in 
diameter  to  fit  tightly,  as  a  cover  on  the  top  of  the 
stove,  should  be  ordered  at  the  tinsmith's. 

Figure  1  represents  the  dome  with  the  smoke-pipe 
attached.    The  pipe  should  be  self-supported,  so  that 

Fig  1. 


THE  reducer's  MANUAL. 


33 


the  dome  may  be  lifted  on  or  off  to  supply  fuel,  or  to 
observe  the  progress  of  the  operation. 

Figure  2  represents  this  arrangement  complete.  A 
is  the  cylinder  stove,  of  which  the  smoke-pipe  B  is 
plugged  up  with  fire-clay  ;  C  is  the  funnel-shaped. 


Fig.  2. 


sheet-iron  dome,  tapering  off  into  the  smoke-pipe  D; 
E  E  are  two  handles  which  may  be  attached  to  the 
dome  to  facilitate  its  removal.  The  great  simplicity  of 
this  arrangement  can  be  seen  at  a  glance. 

A  Blast  Furnace  is  constructed  by  setting  a  cylinder 
stove,  with  smoke-pipe  attached,  in  the  ordinary  man- 
ner, closing  the  draft  hole  below  the  grate  with  a  piece 
of  sheet-iron,  having  a  circular  hole  large  enough  to 
admit  the  nozzle  of  a  pair  of  bellows,  or  rotating-fan 
arrangement.  Of  these  two  methods  of  creating  a  cur- 
rent of  wind,  we  decidedly  prefer  the  latter. 


34 


THE  reducer's  MANUAL. 


A  very  simple  and  efficient  rotating-fan  arrangement 
may  be  made  as  follows  :  Take  a  ribbon-block,  two 
inches  in  diameter,  and  fasten  into  this  at  right  angles 
four  sheets  of  iron  or  stiff  pasteboard,  four  inches 
wide  by  six  long,  or  of  any  size  convenient  to  the  oper- 
ator. A  hole  should  be  drilled  through  the  center  of 
the  block,  and  a  tightly  fitting  wooden  axle  passed 
through  it.  This  arrangement  completed  should  be 
mounted  in  an  airtight  wooden  box,  just  barely  large 
enough  to  admit  of  its  turning  freely,  and  a  crank  at- 
tached on  the  outside  of  the  box  to  one  end  of  the 
spindle.  Two  circular  holes,  about  three-quarters  of 
an  inch  in  diameter,  are  now  cut  at  both  ends  of  the 
box,  one  an  inch  from  the  bottom,  and  the  other  an 
inch  from  the  top;  a  piece  of  iron  gas-pipe,  about  six 
inches  long,  being  firmly  secured  in  the  lower  hole, 
the  arrangement  is  complete. 

Figure  3  represents  a  sectional  view  of  this  wind  ar- 
rangement. A  is  the  ribbon-block;  B  B  B  B  the  four 
sheet-iron  fans;  C  the  spindle  upon  which  the  whole 

Fiff.  3. 


•i 


revolves;  D  the  wrooden  encasement,  into  which  the 
fan  arrangement  closely  fits;  E  represents  the  cranks 


THE  EEDUCER's  MANUAL. 


35 


allowed  to  pass  through  the  wooden  side  of  the  en- 
casement, and  by  which  the  fans  are  S€t  in  rotary- 
motion;  F  the  circular  opening  at  the  back,  one  inch 
from  the  top  of  the  box;  G  the  orifice,  with  a  pipe  at- 
tached, through  which  the  air  is  forced  when  the  wheel 
is  in  motion. 

When  the  fans  are  rapidly  turned  by  the  crank  a 
strong  and  steady  current  of  air  is  forced  through  the 
outlet.  When  it  is  required  to  use  the  blast,  the  out- 
let tube  of  the  fan  arrangement  is  allowed  to  project 
through  the  circular  hole  in  the  sheet-iron,  placed  be- 
fore the  draft-hole  of  the  circular  stove,  and  the  con- 
nections are  made  perfectly  airtight  by  a  lute  of  fire- 
clay or  putty.  If  the  fan  is  now  set  in  motion  the  air 
is  forced  through  the  fire,  causing  it  to  burn  with  the 
greatest  intensity.  The  power  of  this  little  device  is 
wonderful;  and  we  have  frequently  brought  a  mass  of 
gold,  weighing  twenty  ounces,  to  thorough  fusion  in 
five  to  seven  minutes. 

When  a  cylinder  stove  cannot  be  readily  obtained, 
a  very  cheap  and  efficient  furnace  may  be  put  together 
as  follows :  Take  a  piece  of  stove-pipe,  eight  to  ten 
inches  in  diameter  and  ten  to  twelve  inches  in  height, 
and  line  it  evenly  from  top  to  bottom,  to  the  thickness 
of  about  one  inch  with  fire-clay,*  or,  in  default  of  this, 
with  a  mixture  of  equal  parts  of  kaolin  or  pipe-clay 
and  fine  white  sand. 

This  mixture  should  be  made  into  an  even,  smooth 
dough  or  batter  with  water.  Previous  to  the  lining, 
however,  a  circular  hole  should  be  cut  large  enough  to 

*  Fire-clay  of  the  consistency  of  thick  dough  may  be  obtained  at  any 
fire-brick  factory. 


36 


THE  EEDUCER's  MANUAL. 


admit  the  nozzle  of  the  rotating-fan  arrangement,  and 
about  one  inch  from  the  bottom;  or  it  might  be  pro- 
vided with  a  small  door  to  admit  the  draft,  if  used  as 
a  wind  or  reverberatory  furnace.  This  being  done,  a 
series  of  short,  stout  pieces  of  wire,  from  one-eighth  to 
one-fourth  of  an  inch  in  thickness,  should  be  embedded 
in  the  fire-clay,  about  one  inch  from  the  draft-hole,  to 
serve  as  a  grate.  For  convenience'  sake,  three  sheet- 
iron  legs  should  be  riveted  to  the  body  of  the  furnace, 
so  as  to  raise  it  six  to  eight  inches  from  the  ground. 
The  bottom  is  provided  with  a  movable  sheet-iron  cap, 
like  those  on  blacking-boxes,  to  render  the  removal 
of  the  ashes  more  easy.  The  top  being  furnished  with 
a  movable  sheet-iron  dome  and  smoke-pipe,  communi- 
cating with  the  chimney,  the  furnace  is  complete. 

This  simple  little  device  is  admirably  adapted  to  the 
wants  of  the  practical  photographer,  being  small,  neat, 
compact  and  very  efficient.  Used  in  connection  with 
the  wind  arrangement,  it  is  capable  of  melting  steel  in 
from  fifteen  to  twenty  minutes.  In  many  cases,  however, 
it  may  be  more  convenient  to  buy  a  complete  reducing 
furnace.  The  neatest  and  most  economical  of  the 
ready  made  furnaces,  is  that  known  as  Kent's,  which 
has  all  the  appliances,  so  that  it  may  easily  be  changed 
into  either  wind,  blast  or  reverberatory  furnace. 

SELECTION  AND  PREPARATION  OF  FUEL. 

Coal,  coke  or  charcoal  is  the  fuel  most  generally  used 
in  furnace  operations.  Coal  is  the  least  available  as 
it  yields  a  large  amount  of  ash  and  chnker,  which 
choke  the  grating  and  seriously  impede  the  draft. 
Coke  or  charcoal  are,  therefore,  decidedly  to  be  pre- 


THE  reducer's  MANUAL. 


37 


ferred  in  furnace  operations.  Weight  for  weiglit,  their 
amount  of  heat  is  almost  equal;  but  the  much  greater 
density  of  coke  enables  it,  bulk  for  bulk,  to  give  a 
greater  heat  by  ten  per  cent.  For  all  operations  re- 
quiring a  high  heat,  we  prefer  to  use  coke,  as,  when  it 
is  of  good  quahty,  it  yields  but  Httle  cHnker  and  ash, 
and  gives  an  intense  and  steady  heat.  Whether  coke, 
coal  or  charcoal  be  used,  they  should  be  broken  into 
pieces  of  the  size  of  a  large  walnut,  so  that  they  may 
not  pack  too  tightly  nor  too  loosely  around  the  cru- 
cible when  in  the  fire. 

A  mixed  fuel  has  many  advantages  over  any  single 
one  of  the  above-named  fuels.  The  following  will  be 
found  among  the  best:  Coke,  one  bushel;  charcoal, 
one  peck.  Or  coke,  one  bushel;  charcoal,  one  peck; 
hard  coal,  one-half  peck.  Or  charcoal,  one  bushel;  coke, 
one  bushel;  and  coal,  one-half  bushel.  These  materials 
should  be  previously  pounded  to  the  proper  size  and 
thoroughly  mixed.  They  are  considerably  improved, 
if  they  are  to  be  used  without  blast,  by  being  moist- 
ened with  water,  containing  one  ounce  of  niter  to  the 
gallon,  and  then  dried  thoroughly. 

CRUCIBLES  AND  MELTING-POT. 

The  vessels  or  receptacles  used  in  fusing,  or  smelt- 
ing substances,  are  called  crucibles.  The  Hessian  or 
French  crucibles  are  those  most  generally  used.  The 
Hessian,  so  called  from  their  place  of  manufacture,  are 
of  a  tapering  form,  either  round  or  triangular,  and 
come  in  nests,  gradually  increasing  in  size,  from  one- 
half  ounce  upward.  They  are  made  of  a  very  refract- 
ory and  durable  material,  and,  being  very  cheap,  are 
2 


38 


THE  reducer's  MANUAL. 


preferred  to  all  others.  The  Plumbago  or  Black  Lead 
crucibles  are  suitable  for  refining  only,  and  should  not 
be  used  in  reducing  operations.  The  eight  or  ten 
ounce  sand  crucibles  are  those  most  convenient;  being 
much  thinner  than  the  larger  ones,  the  reduction  may 
be  performed  in  a  much  shorter  time,  and  the  cost  of 
these  is  but  a  few  cents.  The  French  crucibles  have 
but  one  fault,  namely,  their  high  price,  which  excludes 
them  entirely  from  common  use. 

We  close  this  chapter  by  giving  a  list  of  what  is  re- 
quired for  a  complete  furnace  outfit,  the  whole  of  which 
will  not  cost  more  than  five  dollars. 

A  small  furnace  or  cylinder  stove,  fitted  up  as  above 
described. 

A  fan  blast  arrangement,  or  a  pair  of  double  acting 
bellows. 

One  or  two  pair  of  iron  tongs,  stout  but  not  too 
heavy. 

Several  Hessian  sand  crucibles  with  covers. 

Several  lengths  of  clean,  stout  iron  wire  with  which 
to  stir  the  fused  mass. 

Some  fire-clay,  or  putty,  to  be  used  as  lute,  in  the 
blast  arrangement. 


CHAPTEK  III. 


ON  THE  BEST  METHODS  AND  APPAEATUS  FOR  SAVING  THE 
VARIOUS  WASTES  OCCURRING  IN  PHOTOGRAPHY. 

We  shall  in  this  chapter  describe  the  methods  em- 
ployed in  saving  the  various  wastes  and  residues,  in 
the  order  in  which  they  are  produced,  in  the  different 
photographic  manipulations.  "We  will  begin  with  the 
preparation  of  the  bath  for  sensitizing  the  plate,  and 
proceed  with  the  description  to  the  toned  and  fin- 
ished print,  with  a  view  to  the  greatest  economy  and 
saving  of  the  precious  metal,  in  all  the  necessary  oper- 
ations. 

the  BATH. 

In  the  preparation  of  the  bath,  it  is  customary  to 
saturate  the  solution  of  nitrate  of  silver  with  an  iodide 
or  a  bromide  to  prevent  the  blemishes  upon  the  plate, 
known  as  pinholes.  The  canary  yellow  precipitate, 
produced  by  the  addition  of  one  of  these  reagents, 
consists  of  pure  iodide  or  bromide  of  silver,  which 
should  be  carefully  saved.  It  is  best  removed  from 
the  solution  by  filtration  through  paper.  The  paper 
used  in  this  operation,  of  course,  becomes  saturated 
with  the  solution,  and  acquires  a  large  percentage  of 
silver. 

The  filter,  with  its  contents,  should  be  well  dried, 
and  carefully  preserved  in  a  covered  wooden  box. 


40 


THE  reducer's  MANUAL. 


THE  SENSITIZED  PLATE. 

The  sensitized  plate,  before  being  placed  into  the 
holder,  should  be  thoroughly  wiped  on  the  back  from 
all  adhering  solution;  a  pad  or  cushion  may  be  placed 
near  the  bath  for  this  special  purpose,  and  a  large  sav- 
ing attained  by  this  simple  device.  A  roll  or  pad  of 
blotting-paper  may  be  advantageously  substituted  for 
•the  cotton.  By  simply  drawing  the  back  of  the  plates 
across  it,  when  removed  from  the  bath,  the  cushion 
becomes  saturated  with  crystals  of  nitrate  of  silver  in 
a  short  time. 

A  clean,  porous,  cotton  cloth  should  be  placed,  or 
hung,  in  a  convenient  proximity  to  the  plateholder, 
the  corners  of  which  should  be  carefully  and  thor- 
oughly wiped  dry  from  adhering  solution  after  each 
exposure.  This  operation  should  never  be  omitted,  as 
better  photographic  results,  as  well  as  greater  econ- 
omy, are  thus  obtained.  Whenever  a  sensitized  plate, 
either  before  or  after  development,  becomes  useless 
from  any  cause,  the  collodion  film  should  be  carefully 
removed  from  the  plate,  and  thrown  into  a  bottle  con- 
taining salt  water.  If  it  is  desired  to  reduce  these 
films  by  the  wet  method,  in  preference  to  fusion,  the 
undeveloped  and  developed  should  be  kept  apart, 
otherwise  they  may  be  mixed. 

DEVELOPER  RESIDUES. 

When  developing  a  plate,  all  superfluous  solution 
from  the  same  should  be  allowed  to  drain  into  a  bottle, 
kept  separately  for  this  purpose.  When  the  develop- 
ment is  finished,  the  plate  should  be  flowed  with  a 
small  amount  of  water,  which  is  allowed  to  drain  into 


THE  reducer's  IVIANUAL. 


41 


tlie  same  bottle;  the  plate  may  then  be  thoroughly 
washed  under  the  tap.  In  large  galleries,  where  a 
considerable  number  of  plates  are  developed,  a  small, 
watertight  tank  of  sheet-iron,  or  cemented  wood,  may 
be  substituted  for  the  bottle. 

THE  FIXING  SOLUTION. 

The  print  fixing  solution,  whether  hyposulphite  of 
soda,  or  cyanide  of  potassa,  should,  when  too  weak  for 
fixing  purposes,  be  placed  in  a  stoppered  bottle  and 
labeled  accordingly. 

"When  removing  a  plate  from  the  fixing  bath,  it  should 
be  held  for  some  time  in  an  upright  position,  so  that  all 
superfluous  solution  may  trickle  back  and  be  retained. 
If,  after  fixing,  the  plate  is  accidentally  scratched,  or 
otherwise  rendered  unfit  for  use,  the  film  may  be 
scraped  off  and  preserved  in  a  separate  bottle. 

OLD  NEGATIVES,  AMBROTYPES,  ETC.,  ETC. 

When  it  is  desired  to  again  use  the  plates  upon 
which  negatives  or  positives  have  been  taken,  the 
silver  contained  in  the  film  of  the  picture  may  also  be 
regained,  to  do  which  proceed  as  follows: 

Half  fill  a  deep  earthen  dish  with  the  following  so- 
lution: 

Caustic  potash  -      -      -      -     8  ounces. 
Water      -      -      -      -      -   16  " 

OR, 

Carbonate  of  potash  -      -      -   10  ounces. 
Boiling  water    -      -      -      -   15  " 

Into  either  of  these  solutions,  preferably  the  first, 
place,  face  downward,  a  number  of  negatives,  one  upon 


42 


THE  reducer's  MANUAL. 


another,  until  tlie  disli  is  full.  The  negatives  are  al- 
lowed to  remain  from  one  to  four  hours,  after  which 
time  the  varnish  will  be  completely  softened,  and  the 
whole  film  may  be  readily  removed  with  the  fingers, 
and  placed  unwashe,d  into  a  clean  labeled  bottle. 

The  plates,  if  intended  to  be  reused  for  the  produc- 
tion of  a  picture,  must,  after  this  operation,  be  washed 
with  dilute  nitric  acid,  to  remove  all  superfluous  alkali, 
well  washed,  and  finally  rubbed  dry  with  a  clean  cloth. 
By  these  means  a  brilliantly  clean  plate  is  obtained. 

PAPER  CLIPPINGS,  ETC.,  ETC. 

The  filters  and  residues  obtained  in  sensitizing 
paper,  should  be  carefully  saved.  All  untoned  paper 
contains  a  large  amount  of  silver,  in  the  form  of  chlo- 
ride, and  furnishes  one  of  the  richest  and  most  valu- 
able residues  obtained  in  the  gallery.  For  the  sake  of 
economy,  especially  in  larger  establishments,  the  prints 
should  be  cut  to  the  proper  size,  as  they  are  removed 
from  the  frame,  before  toning,  as  thus  a  large  amount 
of  valuable  clippings  are  obtained,  the  silver  on  which 
is  otherwise  lost  in  the  toning  and  fixing  solution,  from 
which  it  cannot  be  so  readily  regained.  Paper  filters  and 
filtering  cotton  are  the  richest  of  the  paper  wastes,  con- 
taining generally  from  forty  to  sixty  per  cent,  of  silver, 
according  to  the  number  of  times  the  silver  solution 
has  been  passed  through  them.  The  drippings  of  the 
sensitized  sheets  of  pa^oer  should  be  received  upon 
sheets  of  newspaper,  which  may  remain  there  until 
they  become  saturated  by  the  solution. 

THE  PRINT  WASHINGS. 

On  removing  the  prints  from  the  frame,  they  should 


THE  BEDUCEr's  MANUAL. 


43 


be  placed  in  a  small  tank  of  water  and  thorougUy 
shaken  or  agitated  for  a  few  minutes. 

The  milky  liquid  resulting,  is  poured  into  a  clean 
barrel,  and  the  operation  repeated  several  times,  or 
until  the  water  ceases  to  show  a  milky  turbidity.  In 
each  case  the  smallest  possible  amount  of  water  should 
be  used,  say  one  gallon  to  each  hundred  pints.  Three 
washings  will  generally  suffice,  and  the  prints  may  then 
be  thoroughly  washed  in  abundance  of  water,  without 
any  further  loss  of  silver.  About  a  pint  of  the  follow- 
ing solution  should  be  added  to  the  washings  of  each 
hundred  prints. 

"Water  1  pint. 

Common  salt,  to  thorough  saturation. 

The  barrel  and  its  contents  should  be  thoroughly 
stirred  or  shaken  after  each  addition  of  the  salt  water. 

The  salt  solution  should  not  be  added  to  the  water, 
in  which  the  prints  are  washed,  as  is  customary  with 
some,  as  it  only  tends  to  form  the  insoluble  chloride 
within  the  fibers  of  the  paper  and  decreases  the  amount 
of  the  soluble  silver;  but,  on  the  contrary,  the  purest 
soft  water  should  be  selected  for  the  purpose.  Care 
should  be  taken  that  no  waste  hyposulphite  or  cyanide 
finds  its  way  into  the  barrel  containing  the  print 
washings. 

THE  TOKING  SOLUTION. 

When  the  toning  solution  becomes  unfit  for  use,  it 
should  be  poured  into  a  large  stoppered  bottle  and 
carefully  preserved.  It  contains  a  small  amount  of 
gold  and  silver.  We  once  obtained  twenty  dollars' 
worth  of  pure  gold  from  the  six  months'  saving  of  a 


44 


THE  reducer's  MANUAL. 


gallery.  The  toning  bath  residue  may  be  treated 
equally  well,  either  by  the  dry  or  wet  methods  of  re- 
duction, as  will  be  hereafter  described. 

THE  PRINT  FIXING  SOLUTION. 

The  print  fixing  solution,  when  it  becomes  weakened 
by  use,  contains  a  considerable  amount  of  hyposul- 
phite of  silver.  The  prints  should  be  well  drained  from 
all  superfluous  hyposulphite  solution  before  they  are 
removed  to  the  washing-tank. 

It  is  customary  in  some  galleries  to  add  fresh 
hyposulphite  of  soda,  as  the  old  solution  becomes 
weakened  in  action;  this  is,  however,  false  economy; 
the  prints  are  never  so  perfect  or  lasting  when  this 
method  is  resorted  to.  The  old  solution  should  be 
poured  into  a  barrel  or  demijohn,  properly  labeled  for 
future  treatment,  when  enough  has  accumulated. 

THE  APPARATUS. 

The  necessary  apparatus  to  carry  out  the  operations 
described  in  this  chapter  is  very  simple.  Several 
funnels,  and  earthen  dishes,  a  few  large,  clean  bottles, 
or  demijohns,  and  a  ten  or  twenty  gallon  barrel,  con- 
stitute the  whole  outfit.  As  a  tank  for  containing  the 
developer  drainings,  a  tightly  dove-tailed,  shallow 
wooden  box  is  procured,  the  sides  and  bottom  of 
which  are  evenly  covered  with  a  thick  varnish  like 
composition,  impervious  to  water  and  made  as  follows: 

Best  yellow  resin      -      -  -  16  ounces. 

Yellow  beeswax  -      -      -  -  12  " 

Turpentine       -      -      -  -  4  « 
Lamp-black,  enough  to  color. 


THE  BEDUCER's  MANUAL. 


45 


The  wax  and  resin  are  melted  together  in  a  tin  pot, 
and,  when  perfectly  liquid,  the  turpentine  is  stirred 
in.  The  mixture  must  be  applied  hot.  The  barrel 
containing  the  print  washings  should  be  provided  with 
a  stopcock  or  faucet,  placed  about  twelve  inches,  in- 
stead of  two  inches,  from  the  bottom  of  the  barrel. 
When  the  curdy  precipitate  has  settled  to  the  bottom 
(for  which  the  liquid  should  remain  at  rest  for  at  least 
twenty-four  hours),  the  sides  are  gently  thumped  all 
around  with  a  mallet  or  hammer,  so  that  the  precipi- 
tate, clinging  to  the  sides  of  the  barrel,  is  disengaged. 
The  faucet  may  then  be  turned  on  and  all  the  super- 
fluous water  allowed  to  flow  out.  This  operation  can 
be  continued  until  the  precipitated  chloride  reaches 
the  height  of  the  stopcock. 

A  few  glass  syphons,  or  a  yard  of  narrow  rubber 
tube,  should  be  provided,  which  form  a  convenient 
method  of  removing  the  water  from  above  an  easily 
disturbed  precipitate. 

For  the  solid  wastes,  several  clean,  wooden  boxes, 
with  tightly  fitting  covers,  properly  labeled,  should  be 
kept  in  a  convenient  place. 

W e  would  here  enjoin  upon  the  photographer  to  keep 
each  residue,  either  liquid  or  solid,  in  a  separate  bottle 
or  box.  To  avoid  mistakes,  these  should  be  labeled  re- 
spectively, viz.  :  Collodion  Films,  Developer  Eesidues, 
etc.,  etc.  Some  photographers  have  a  habit  of  mixing 
indiscriminately  together  the  most  diverse  compounds 
obtained  from  the  various  residues  ;  this  occasions 
much  trouble  and  loss  of  time  in  after  operations,  and 
should  be  carefully  avoided. 


2* 


CHAPTEE  IV. 


TREATMENT  OF  THE  VARIOUS  WASTES  PREPARATORY  TO 
SMELTING. 

Having,  as  we  will  suppose,  collected  a  considerable 
quantity  of  gold  and  silver  residues,  the  next  step  is  to 
prepare  them  for  the  crucible.  For  this  purpose  the 
solid  wastes  are  reduced  to  ashes,  and  those  of  a  liquid 
nature  brought  to  a  solid  condition  by  precipitation. 

BURNING  PAPER  WASTES. 

A  great  deal  depends  upon  the  proper  burning  of 
the  paper  residues,  and  it  is  necessary  that  we  enter 
a  little  more  closely  upon  this  subject.  To  insure  a 
perfect  combustion,  it  is  necessary  that  the  air  has  free 
access  to  the  burning  mass.  The  most  convenient 
method  to  insure  this  result,  is  to  burn  the  paper  in  a 
fireplace  grate.  The  grate  is  filled  loosely  with  the 
clippings,  old  filtering-paper,  etc.,  etc.,  which  is  then 
ignited,  and,  when  it  has  burned  down  to  a  glowing 
heap  of  ashes,  the  rest  of  the  paper  is  fed  very  slowly 
by  handfuUs,  so  as  not  to  suffocate  the  flame  for  an  in- 
stant. The  ashes  should  be  carefully  raked  into  an 
iron  iDan  when  they  begin  to  choke  the  draft,  and  spread 
thinly,  so  as  to  allow  them  to  glimmer  on.  By  these 
means  a  very  perfect  combustion  is  insured.  When 
well  burnt,  the  ashes  should  have  a  whitish  gray  color, 
without  any  black  or  carbonaceous  residue;  should  be 


THE  BEDUCERS  MANUAL. 


47 


friable  and  easily  reduced  to  a  fine  powder  by  friction 
between  the  fingers.  The  richer  the  ashes  in  silver, 
the  whiter  and  more  metallic  they  will  be  in  color.  In 
the  ashes  of  filtering-paper,  large  granules  or  spangles 
of  metallic  silver  are  sometimes  found.  Those  who 
cannot  easily  obtain  the  use  of  an  open  grate,  should 
burn  the  paper  in  a  small  cyHnder  stove,  or  in  a  clay 
or  iron  fire-bucket.  In  using  a  stove  with  a  good  draft, 
care  should  be  taken  that  none  of  the  ashes  are  whirled 
up  the  chimney,  as  a  great  loss  can  be  occasioned 
thereby.  Filters,  filtering-cotton,  cloth,  untoned  clip- 
pings and  other  paper  residues  may  be  all  mixed  to- 
gether. It  is  not  necessary  to  keep  these  separate, 
as  practiced  by  some,  except  when  the  paper  is  sold  to 
re&ners  or  smelters.  It  is  always  advantageous  when 
cloth  or  paper,  poor  in  silver,  are  burned,  to  moisten 
them  with  either  of  the  following  solutions,  which  in- 
sures a  much  more  perfect  combustion: 

Nitrate  of  potash  (saltpeter)     -     6  ounces. 
Water  16  " 

OR, 

Chlorate  of  potash     -      -       -     4  ounces. 
Water  16  " 

Of  these  two  sohitions  the  first  is  the  cheapest,  and 
T3oth  are  equally  efficient. 

The  paper,  or  cotton,  as  the  case  may  be,  should  be 
sprinkled  with  one  of  the  solutions,  until  thoroughly 
dampened  through,  and  then  perfectly  dried  by  the 
heat  of  the  sun  or  a  gentle  fire.  When  ignited  in  a 
stove,  the  paper  thus  prepared,  be"  it  ever  so  poor  in 
silver,  burns  with  intensity. 


48 


THE  reducer's  MANUAL. 


TREATMENT  OF  DEVELOPER  WASHINGS. 

The  turbid  liquid  gathered  from  the  plate  washings 
is  mixed  with  a  strong  solution  of  common  salt,  and 
exposed  for  several  days  to  bright  sunshine;  at  the 
end  of  this  time  the  liquid  will  generally  be  found 
clear,  and  a  black  precipitate  to  have  subsided  to  the 
bottom,  which  consists  of  a  mixture  of  metallic  silver 
and  iron.  The  bottle  should  be  well  shaken,  and  the 
whole  contents  poured  upon  a  paper  jSlter  and  allowed 
to  dry.  Another  method  is  to  add  to  the  "  washings  " 
a  solution  of  sulphide  of  potash,  until  it  ceases  to  give 
a  black  coloration  in  the  liquid;  it  is  then  likewise 
thrown  upon  a  JGilter  and  allowed  to  dry.  The  precipi- 
tates thus  prepared  are  ready  for  the  crucible.  Of  these 
two  methods  we  prefer  the  first. 

OLD  COLLODION  FILMS. 

To  prepare  these  in  the  best  manner,  they  should  be 
first  thoroughly  dried  and  then  sprinkled  with  either  of 
the  solutions  recommended,  on  the  last  page,  for  paper 
clippings,  the  last  of  which  is  preferable.  After  hav- 
ing thoroughly  dried  them,  they  are  placed  upon  an 
iron  shovel  or  pan  and  ignited  with  a  glowing  coal, 
when  they  will  be  reduced  to  a  fine  yellow  ash.  The 
most  convenient  method  of  separating  the  water,  or 
adherent  solution,  from  old  films,  is  to  throw  them, 
when  removed  from  the  plate,  upon  a  fine  cloth  filter, 
suspended  in  the  neck  of  a  wide-mouthed  bottle.  The 
solution  flows  through,  and  may  be  afterward  precipi- 
tated with  common  salt,  while  the  solid  films  are  left 
upon  the  cloth  to  dry.  The  films  obtained  in  the  vari- 
ous stages  of  the  process,  should  be  kept  apart.  Thus, 


THE  EEDUCEr's  MANUAL. 


49 


those  obtained  before  development,  contain  a  large 
amount  of  iodide  and  bromide  of  silver,  as  also  con- 
siderable unused  nitrate  of  silver;  those  after  develop- 
ment, metallic  silver,  iron  and  nitrate  of  silver;  while 
those  obtained  after  fixing,  or  when  reusing  an  old 
plate,  contain  onlij  metallic  silver,  with  a  solution  of 
hyposulphite  of  soda,  or  caustic  potash,  as  the  case 
may  be.  It  would,  therefore,  be  convenient  to  have 
four  different  bottles  for  the  reception  of  the  various 
films;  each  should  be  properly  labeled,  and  in  no  case 
should  they  be  mixed  together. 

THE  HYPOSULPHITE  FIXING  BATHS. 

When  a  sufficient  quantity  of  this  solution  has  ac- 
cumulated, either  from  the  prints  or  plates,  it  should 
be  placed  into  an  open  barrel,  a  large  wooden  tank,  or 
any  other  convenient  vessel,  and  a  solution  of  sulphide 
of  potash  added  as  long  as  it  produces  a  black  precipi- 
tate or  coloration;  the  liquid  is  then  allowed  to  re- 
main at  rest  for  a  few  days;  and  when  the  solution  is 
perfectly  clear,  as  much  water  as  possible,  without  dis- 
turbing the  precipitate,  is  drawn  off.  The  muddy  re- 
sidue is  poured  upon  a  large  filter,  and  the  precipitate, 
after  being  thoroughly  washed  with  warm  water,  is  al- 
lowed to  dry. 

The  black  mass  thus  obtained,  which  consists  of 
sulphide  of  silver,  should  be  placed  on  an  iron  pan  or 
shovel  and  exposed  to  a  brisk  heat  over  a  lively  coal 
fire.  This  operation  must  be  conducted  either  in  the 
open  air  or  in  a  fireplace,  as  thick  vapors  of  sulphur 
are  generated  during  this  process  of  ignition,  or  roast- 
ing, as  it  is  termed. 


50 


THE  KEDUCERS  MANUAL. 


When  the  black  mass  has  been  exposed  to  a  red  heat 
for  a  few  minutes,  and  has  fused  into  an  even  "  glass/' 
and  all  vapor  ceased,  the  shovel  or  pan  may  be  re- 
moved from  the  fire  and  its  contents  allowed  to  cool. 

This  operation  may  be  dispensed  with  when  the  iron 
flux,  as  recommended  in  the  next  chapter,  is  made  use 
of,  or  when  the  sulphide  is  obtained  from  the  devel- 
oper washings,  as  these  already  contain  the  amount  of 
iron  requisite.  Pure  sulphide  of  silver  yields  about 
half  its  weight  of  metallic  silver. 

TREATMENT  OF  THE  CYANIPE  FIXING  SOLUTION. 

It  has  been  generally  customary  to  throw  away  waste 
cyanide  fixing  solutions,  as  they  became  weak  by  use. 
They,  contain,  however,  a  large  amount  of  silver,  which 
may  be  readily  and  economically  utilized.  The  precipi- 
tation of  silver  from  a  solution  of  its  cyanide,  depends, 
of  course,  on  the  addition  of  a  reagent,  having  a  stronger 
chemical  afiinity  for  the  silver  than  the  cyanic  acid 
with  which  it  is  combined  in  the  solution.  This  ma- 
nipulation is  attended  with  considerable  danger,  owing 
to  the  large  amount  of  cyanic  acid  gas,  a  most  potent 
poison,  which  is  evolved  during  the  operation.  But 
with  proper  management  and  care,  not  only  the  silver, 
but  the  active  principle  of  the  cyanide  of  potash,  may 
be  regained  from  such  waste  solutions. 

Take  a  wide-mouthed  bottle,  of  about  two  quarts 
capacity,  into  the  neck  of  which  fit  a  smooth  and  very 
tight  cork,  through  which  pass  two  glass  tubes,  one 
reaching  within  a  few  lines  of  the  bottom  of  the  bottle 
and  projecting  an  inch  over  the  cork,  the  other  passing 
only  about  half  an  inch  through  the  cork  and  bent  at 


THE  reducer's  MANUAL. 


51 


right  angles  on  tlie  outside.  The  neck  of  a  small  fun- 
nel is  secured  to  the  top  of  the  longest  tube  by  means 
of  a  little  wax.  Figure  4  represents  this  arrangement. 
A  second  bottle  which  may  be  about  half  the  size  of 
the  former,  is  provided  with  a  tight  cork  and  a  glass 


tube  of  the  same  diameter  as  the  last  (which  should  be 
about  a  quarter  of  an  inch),  is  let  through  this  until  it 
reaches  within  the  fourth  of  an  inch  of  the  bottom,  and 
like  the  former  is  bent  at  right  angles.  Having  com- 
pleted this  arrangement,  half  fill  the  first  bottle  with 
the  waste  cyanide  solution,  and  into  the  second  one 
place  a  solution  consisting  of — 

Pure  caustic  potash  -      -      -     4  ounces. 

Watet       -      -      -      -      -     1     "  • 
And  make  the  cork  and  joints  of  both  bottles  perfectly 
airtight  by  brushing  over  the  following  mixture : 

Beeswax    -----     2  ounces. 

Resin       -----       J  ounce. 

Turpentine       -       -       -       -       J  " 

Vermilion,  enough  to  color. 
Place  the  wax  and  resin  on  the  fire  in  a  tin  vessel, 


Fig.  4. 


52 


THE  KEDUCEr's  MANUAL. 


and  when  thoronglily  melted,  stir  in  the  turpentine  and 
vermiHon.  The  latter  is  only  for  appearance  and  may 
be  omitted. 

Figure  5  represents  the  complete  arrangement.  A 
is  the  larger  bottle  containing  the  waste  cyanide  solu- 
tion; B  the  longer  tube  with  the  funnel  attached;  C 
the  shorter  tube  connecting  with  the  rubber-pipe  D, 
through  which  the  cyanic  acid  gas  evolved  is  lead  by 
means  of  the  glass  tube  E  into  the  solution  of  pure 
potash  F. 

Fig.  5. 


Having  concluded  these  prehminary  arrangements, 
common  hydrochloric  or  muriatic  acid  should  be 
slowly  added  to  the  cyanide  solution  in  the  larger 
bottle  by  means  of  the  small  funnel.  Upon  each  ad- 
dition of  the  acid  the  solution  foams  and  scathes  vio- 
lently, and  care  should  be  taken  that  it  does  not  boil 
over.  Simultaneously  with  the  addition  of  the  acid,  a 
white,  curdy  precipitate  of  chloride  of  silver  is  formed, 
which,  however,  is  at  first  redissolved  as  it  descends 
into  the  solution.  Acid  should  be  added  as  long  as  it 
occasions  the  slightest  precipitate  or  foaming  in  the 
solution,  or  until  it  is  considerably  in  the  access.  At 


THE  reducer's  MANUAL. 


53 


the  close  of  the  operation  a  heavy  precipitate  of  pure 
chloride  of  silver  is  found  in  the  first  bottle,  and  a  so- 
lution of  cyanide  of  potash  in  the  other.  If,  after  the 
close  of  the  operation,  the  solution  of  cyanide  of  pot- 
ash in  the  smaller  bottle  should  be  somewhat  weak, 
another  quantity  of  the  waste  cyanide  solution  may  be 
treated  with  acid  and  the  resulting  gas  allowed  to  pass 
into  the  weak  liquid.  It,  however,  generally  happens 
that  the  fresh  cyanide  solution  obtained  by  this 
method  is  too  strong  for  photographic  purposes;  in 
that  case  it  may  be  simply  diluted  with  water.  This 
process  works  very  beautifully  and  the  resulting  sub- 
stances are  nearly  chemically  pure.  When  it  is  de- 
sired to  save  the  silver  only,  the  waste  cyanide  solu- 
tion may  be  precipitated  in  an  open  vessel  with  strong 
hydrochloric  acid  as  before  mentioned;  but  the  opera- 
tion should  be  conducted  in  an  open  place  with  the 
back  against  a  strong  draft  of  wind,  so  that  the  pois- 
onous fumes  arising  may  be  carried  away  from  the 
operator.  We  would  recommend,  however,  the  first 
process  as  the  best,  having  used  it  with  great  success 
in  the  reductions  of  the  waste  cyanide  solutions,  oc- 
curring m  the  electro-plating  art. 

Another  very  excellent  method  of  utilizing  the  cyan- 
ide solutions,  is  to  evaporate  them  to  dryness.  By 
these  means  a  solid  is  obtained  (containing  all  the 
silver),  which  may  be  employed  with  the  greatest  suc- 
cess as  a  flux  for  the  reduction  of  sulphide  of  silver  and 
other  wastes.  In  evaporating  the  solution  great  care 
is  also  necessary,  as  fumes  of  prussic  acid  are  given  oflf. 
The  evaporation  should  be  conducted  either  in  a  fire- 
place or  in  the  open  air. 


54 


THE  reducer's  MANUAL. 


HOW  TO  PRECIPITATE  THE  TONING  BATH. 

At  least  three  gallons  of  tlie  waste  baths  should  have 
accumulated  before  it  is  worth  while  to  undertake  their 
precipitation;  then  place  it  in  a  wide-mouthed  glass 
vessel,  and  add  the  following  solution  in  small  quanti- 
ties, until  it  ceases  to  give  a  black  precipitate : 

Sulphate  of  iron       -      -      -     4  ounces. 
Water  16  " 

Allow  the  now  jet  black  solution  to  remain  at  rest 
for  several  days,  or  until  the  precipitate  has  entirely 
subsided  to  the  bottom ;  then  add  a  few  drops  of  the 
iron  solution  to  the  clear  liquid,  and  if  no  further  pre- 
cipitatQ  is  occasioned  thereby,  the  operation  is  com- 
plete. Filter  and  dry  the  ebony  black  powder  thus 
obtained,  which  consists  of  a  mixture  of  metallic  gold, 
iron  and  the  oxide  of  iron,  and  expose  it  to  a  red  heat 
in  an  iron  shovel  or  other  convenient  vessel.  By  these 
means  the  whole  of  the  iron  is  changed  into  the  sesqui- 
oxide,  thus  rendering  its  removal  very  easy.  When 
quite  cold,  place  the  now  dark  red  powder  in  an  evap- 
orating-dish,  and  pour  upon  it  some  pure  hydrochloric 
acid  and  heat  the  vessel  gently.  The  solution  of  the 
iron  immediately  takes  place,  and  when  the  scathing 
has  ceased,  dilute  the  mass  with  cold  water,  throw  the 
contents  of  the  dish  upon  a  filter,  and  wash  the  re- 
maining black  powder  copiously  with  water.  The  re- 
sult is  pure  metallic  gold.  Care  should  be  taken  that 
the  acid  used  in  this  operation  is  pure,  or  does  not 
contain  any  uncombined  gas,  as  this  would  cause  a 
partial  solution  of  the  gold,  and  thus  occasion  loss.  It 
is  not  necessary  to  remove  the  iron,  except  when  the 


THE  reducer's  MANUAL. 


55 


gold  is  to  be  used  for  the  production  of  tlie  cMoride. 
If  the  product  is  to  be  fused,  the  precipitate  obtained 
by  the  addition  of  the  sulphate  of  iron,  may  be  dried 
and  fluxed  without  further  preparation. 

PREPARATION  OF  THE  NITRIC  ACID  PLATE  CLEANING 
SOLUTION. 

When  nitric  -acid  has  been  used  for  removing  old 
films  from  glass  plates,  it  takes  up  a  considerable 
amount  of  metallic  silver;  this  may  be  regained  in  the 
form  of  chloride  by  adding  some  pure  hydrochloric 
acid.  When  potash,  or  its  carbonate  is  employed,  as 
directed  on  page  41,  for  the  removal  of  films,  no  silver 
is  employed,  but  all  is  retained  in  the  films. 

PRECIPITATION  OF  OLD  BATHS,  NITRATE  OF  SILVER  SOLUTIONS, 
ETC.,  ETC. 

When  the  silver  bath  has  become  weak  and  uncertain 
in  its  action,  or  has  been  spoiled  by  accidental  admix- 
ture of  some  foreign  substance,  the  quickest  and  most 
expeditious  method  of  utilizing  it  is  to  precipitate  it. 
This  is  done  by  adding  to  such  residues  a  strong  so- 
lution of  common  salt,  or  some  dilute  hydrochloric 
acid.  If  the  silver  solution  is  pretty  strong,  it  should 
previously  be  diluted  with  an  equal  bulk  of  water,  and 
the  acid  or  salt  added  as  long  as  a  white  precipitate  is 
caused  by  such  addition.  The  result  is  pure  chloride 
of  silver.  It  should  be  thrown  upon  a  filter  and  freely 
washed  with  warm  water.  Chloride  of  silver  may  be 
very  efficiently  reduced  by  the  wet  methods,  as  will  be 
hereafter  described;  but  for  this  purpose  it  must  be 
freshly  precipitated,  or  at  least  not  have  been  allowed 
to  dry.    Chloride  of  silver  which  is  to  be  reduced  in 


56 


THE  REDUCEK's  MANUAL. 


the  humid  way,  may  be  conveniently  kept  in  the  dark- 
room, in  a  bottle  containing  enough  water  to  thor- 
oughly cover  it,  until  a  sufficient  quantity  has  accu- 
mulated. Another  excellent  method  of  treating  waste 
solutions  of  nitrate  of  silver,  which,  however,  is  only 
applicable,  if  intended  for  humid  reduction,  is  to  pre- 
cipitate by  means  of  sulphuric  acid  or  a  sulphate.  The 
following  solution  answers  very  well: 

Sulphate  of  potash    -      -      -     4  ounces. 

"Water  12  " 

Add  it  slowly,  drop  by  drop,  into  the  silver  solution, 
as  long  as  it  produces  a  white  precipitate  or  coloration. 
The  white  powder  resulting,  which  consists  of  sulphate 
of  silver,  after  being  well  washed,  should  be  kept  under 
water  like  the  former.  The  sulphate  of  j)otash,  used  in 
this  formula,  must  not  be  mistaken  for  the  sulphide, 
which  produces  the  black  precipitate  of  sulphide  of 
silver.  From  all  waste  nitrate  of  silver  solutions,  the 
silver  should  be  precipitated  in  the  form  of  chloride, 
and  the  sulphide  avoided  as  much  as  possible,  except 
in  such  cases  where  it  is  indispensable,  as  in  waste  hy- 
posulphate  solutions,  etc.,  etc.  Chloride  of  silver  is 
the  easiest,  sulphide  of  silver  the  hardest  and  most  ob- 
stinate compound  to  reduce. 

GENERAL  REMARKS  AND  PRACTICAL  SUGGESTIONS. 

Frecipitation, 

The  process  of  precipitation,  as  we  have  already 
shown,  is  employed  for  the  immediate  separation  of  a 
body  in  a  solid  state  from  a  chemical  solution.  As 
heat  in  all  cases  promotes  the  subsidence  of  the  pre- 
cipitate, the  solution  may  be  previously  warmed  and 


THE  reducer's  MANUAL. 


57 


the  reagent  added  slowly  and  under  constant  stirring, 
so  that  the  parts  of  the  liquid  may  be  brought  into 
contact.  The  solution  is  then  allowed  to  remain  at 
rest  until  the  deposition  of  the  precipitate  has  left  the 
supernatant  liquid  clear.  A  few  more  drops  of  the  re- 
agent should  now  be  added,  and,  if  no  further  cloudi- 
ness or  precipitate  is  occasioned,  the  operation  is  com- 
plete. 

A  liquid  may  be  precipitated  in  any  convenient  ves- 
sel, but  this  should  preferably  be  of  glass,  as  then  the 
action  and  result  may  be  better  observed.  When  but 
small  quantities  of  a  solution  are  operated  upon,  glass 
vessels  with  tapering  sides,  known  as  precipitating 
glasses  (Figure  6),  may  be  employed  with  advantage. 
The  form  of  these  vessels  is  peculiarly  well  adapted 


Fig.  6. 


for  the  precipitation  of  precious  salts,  as  none  of  the 
precipitate  can  adhere  to  the  sides  of  the  vessel.  When 
a  very  large  quantity  of  solution  is  to  be  precipitated, 
the  operation  is  best  conducted  in  large,  wide-mouthed 
glass  bottles  or  candy-jars,  or  in  glazed  earthen  ves- 
sels, though  the  latter  are  open  to  objection,  on  ac- 
count of  not  being  transparent.  An  excellent  vessel 
for  precipitating  solutions,  is  the  barrel  with  the  fau- 
cet in  the  middle,  as  recommended  on  page  45,  for 


58 


THE  reducer's  MANUAL. 


print  washings.  A  very  thorough,  washing  of  the  pre- 
cipitate is  insured  by  this  simple  device. 

Filtration  and  Decantation, 

The  mode  most  generally  resorted  to  for  the  separ- 
ation of  precipitates  from  liquids  in  which  they  are 
suspended,  is  that  of  filtration.  The  process  consists 
simply  in  passing  the  substance  to  be  operated  upon 
through  some  medium,  fine  enough  to  intercept  any 
soHd  particles,  however  finely  divided,  still  of  sufficient 
porosity  to  allow  water  to  pass  through  readily.  Paper 
is  the  substance  most  generally  used  for  this  purpose. 
The  paper  best  adapted  for  the  filtration  of  the  bulky 
and  heavy  gold  and  silver  precipitates,  is  that  known 
as  German  filtering  paper,  which,  besides  being  very 
strong  in  texture,  allows  the  water  to  run  through  very 
rapidly.  "When  a  precipitate  is  of  a  bulky  nature,  and, 
especially  if  accompanied  by  much  water,  a  plaited 
filter  should  be  made  use  of,  as  it  prevents  a  close  ad- 
hesion of  the  paper  to  the  glass,  thereby  greatly  expe- 
diting the  process. 

To  form  a  plaited  filter,  take  a  square  of  good  por- 
ous paper  and  fold  it  diagonally,  as  in  Figure  7.  Turn 
A  upon  B  to  obtain  the  crease  E,  and  open  it;  then 

Fig.  7. 


THE  KEDUCEk's  MANUAL. 


59 


double  A  upon  E  in  the  same  direction  to  make  crease 
G;  and  holding  this  plait  between  the  fingers,  make 
the  fold  between  F  and  T>;  divide  the  space  between 
E  B  and  B  D  in  the  same  manner. — Morfit, 

Figure  8  shows  the  position  of  the  filter  in  the  fun- 
nel. After  the  filter  has  been  properly  secured  in  the 
funnel,  and  previous  to  the  addition  of  a  liquid  con- 
taining a  precipitate,  the  filter  should  be  thoroughly 
wet  with  some  clean  water,  as  by  these  means  the 
pores  of  the  paper  are  opened,  rendering  the  filter  less 

Fig.  8. 


liable  to  clog  than  if  the  turbid  liquid  were  added 
immediately.  There  are,  however,  some  precipitates, 
like  the  chloride  and  sulphide  of  silver,  which  so  com- 
pletely clog  certain  kinds  of  paper,  as  to  prevent  the 
slightest  passage  of  water.  In  such  cases  a  lag  of 
felt  must  be  made  use  of. 

A  very  convenient  filter  for  chloride  of  silver,  when 


60 


THE  EEDUCER'S  MANUAL. 


large  quantities  are  operated  upon,  is  an  old  felt  hat, 
suspended  from  four  corners  by  means  of  strings, 
wMcli  should  be  fastened  to  the  ceiling,  just  above  the 
sink.  When  paper  is  used  for  filtering  liquids  which 
pass  through  very  slowly,  a  series  of  small  funnels  with 
plaited  filters  should  be  made  use  of.  Large  funnels 
are  objectionable,  as  the  filters  are  very  liable  to  tear 
from  the  weight  of  the  liquid,  having  no  proper  support 
at  the  bottom;  but  this  trouble  may,  in  a  measure,  be 
remedied  by  placing  a  piece  of  cotton  loosely  in  the 
barrel  of  the  funnel,  so  that  it  reaches  to  the  paper, 
and  it  will  now  act  as  a  support  for  the  filter.  Loose 
plugs  of  cotton  alone  are  very  useful. 

When  a  corrosive  liquid  is  to  be  filtered,  as  a  strong 
acid  or  alkali,  a  plug  of  asbestos,  placed  loosely  in  the 
barrel  of  the  funnel,  is  the  only  suitable  medium. 

Decantation  has  the  same  object  as  filtration,  namely, 
the  separation  of  water  from  a  precipitate;  it  is  only 
resorted  to  when  the  sediment  is  very  heavy  and  sub- 
sides readily  to  the  bottom  of  the  vessel  without  being 
easily  agitated,  as,  for  instance,  the  chloride  of  silver. 
It  consists  simply  in  inclining  the  vessel  gently  to  let 
the  supernatant  fluid  run  off,  or  in  draining  it  off  with 
a  syphon.  The  syphon  is  a  very  convenient  little  in- 
strument and  should  always  be  kept  at  hand. 

The  most  simple  form  of  a  syphon  is  a  small  glass 
tube,  bent  so  that  it  has  two  arms  of  unequal  length. 
(Figure  9.)  The  long  arm  maybe  twenty  inches  in 
length,  the  shorter  one  about  fifteen  inches.  The 
syphon  is  fiUed  with  water,  the  mouth  of  the  longer 
arm  closed  with  a  finger,  and  the  shorter  branch  in- 
troduced, mouth  downward,  into  the  liquid  to  be  de- 


THE  eeducer's  manual.  61 

canted,  until  it  nearly  reaches  tlie  level  of  the  precipi- 
tate without  disturbing  it.    Upon  removing  the  finger 

Fig.  9. 


the  liquid  runs  out  in  a  continuous  stream,  and  may- 
be almost  wholly  drawn  off.  If  the  liquid  is  not  in- 
jurious or  unpleasant  to  the  taste,  the  syphon  may  be 
inserted  into  the  liquid  without  previous  filling,  being 
drawn  over  by  suction  with  the  mouth  through  the 
long  end. — Morfit, 

A  small  piec6  of  rubber  gas-tube  makes  an  excellent 
syphon;  it  should  be  filled  with  water  and  placed  into 
the  liquid  in  such  a  manner,  that  the  end  hanging  over 
the  side  of  the  vessel  is  considerably  shorter  than  that 
in  the  liquid.  All  precipitates  should  have  the  super- 
fluous water  decanted  off  before  they  are  thrown  upon 
the  filter,  as  much  time  is  saved  thereby. 

Drying. 

"When  much  of  the  water  contained  in  a  precipitate 
has  drained  through  the  filter,  and  the  precipitate  is 
3 


62 


THE  EEDUCEr'S  MANUAL. 


of  the  consistency  of  butter,  it  should  be  removed  from 
the  filter  with  a  piece  of  glass,  or  a  spatula,  and  spread 
on  a  large  sheet  of  paper  and  allowed  to  dry  sponta- 
neously; or  it  is  thrown  upon  an  earthen  dish  and 
placed  upon  the  stove  until  it  is  completely  dry.  "Where 
there  is  no  ot3casion  to  hurry  up  the  drying,  the  pre- 
cipitate may  be  allowed  to  remain  upon  the  filter  or 
exposed  to  the  sun  on  a  dish.  "When  a  large  amount 
of  chloride  or  sulphide  of  silver  is  to  be  dryed,  it  should 
be  placed  in  a  large  earthen  bowl,  or  porcelain  evapor- 
ating dish,  and  exposed  to  the  naked  fire,  under  con- 
stant stirring,  until  it  is  perfectly  desiccated. 

Boasting. 

Some  substances,  like  the  sulphide  of  silver  and  the 
precipitate  of  the  toning  bath,  must  be  exposed  to  a 
low  red  heat.  This  operation  is  termed  "roasting," 
or  "  ignition,"  and  is  resorted  to  either,  as  in  the  case 
of  sulphide  of  silver,  to  partially  expel  a  substance 
from  a  compound,  or,  as  in  the  case  of  the  toning  bath, 
to  so  modify  one  of  its  constituents  as  to  make  it  sol- 
uble. Most  substances,  when  exposed  to  heat  in  this 
manner,  give  off  disagreeable  odors.  The  operation  is 
therefore  best  conducted  in  the  open  air  or  in  a  fire- 
place. A  small  clay  fire-bucket,  filled  with  burning 
coal,  should  be  used  to  give  the  necessary  heat,  and 
tlie  substances  exposed  to  it  in  a  thin  layer  on  a  shovel 
or  frying-pan.  An  exposure  of  fifteen  minutes  will 
generally  suffice,  if  the  fire  is  lively. 

Evaporation, 

The  evaporation  of  caustic  solutions,  like  the  cyan- 
ide of  potash,  is  best  conducted  in  porcelain  evaporat- 


THE  reducer's  MANUAL. 


63 


ing  dishes.  This  operation  should  also  be  performed 
in  the  open  air  or  well  ventilated  places.  The  solution 
should  be  allowed  to  boil  rapidly,  until  all  the  water 
has  disappeared.  The  dish  is  then  removed  from  the 
fire,  and  the  salt  thus  obtained  placed  in  well  stoppered 
bottles. 

PRECIPITATING  SOLUTIONS. 

For  Developer  Washings, 

Common  salt     -      -      -      -     8  ounces. 
"Water       .      -      .      -      -    20  " 

OR, 

Sulphide  of  potash    -      -      -     4  ounces. 
Water  16  " 

For  Hyposulphite  Fixing  Baths. 


Sulphide  of  potash 
Water 

Sulphide  of  potash 
Water 


OR, 


For  Toning  Bath, 

Sulphate  of  iron 

Water       -      -      -  - 

OR, 

Sulphate  of  iron 

Water      _      -      -  - 

Sulphuric  acid  -       -  - 

OR, 

Protochloride  of  tin  - 
Water      -      -      -  - 


8  ounces. 
24  " 

4  ounces. 
16  " 

4  ounces. 
16  " 

4  ounces. 
20  " 
4  drops. 

1  ounce. 
12  ounces. 


64 


THE  REDUCERS  MANUAL. 


The  last  solution  answers  very  well,  but  is  too  ex- 
pensive for  general  use. 

The  Nitric  Acid  Plate  Solution. 


Hydrocliloric  acid 
Water 

Sulphuric  acid  - 
Water 


OR, 


4  ounces. 
8  " 

4  ounces. 
10  " 


The  last  solution  should  only  be  used  when  the  pre- 
cipitate is  to  be  reduced  in  the  humid  way. 

For  Old  BathSy  Nitrate  of  Silver  Solutions,  etc.,  etc. 


Common  salt 
Water 

Hydrochloric  acid 
Water 

Sulphate  of  potash 
Water 


OR, 


OR, 


8  ounces. 
20  " 

4  ounces. 
4  « 

4  ounces. 
12  " 


The  last  should  only  be  used  when  the  result  is  to 
be  reduced  by  the  wet  method. 


CHAPTEE  V. 


FLUXING    AND  FUSION. 

The  liquifaction  of  a  substance  by  tlie  application 
of  heat,  is  termed  fusion.  Fluxes  are  substances  usu- 
ally of  a  saline  character,  which  are  mixed  with  a  com- 
pound in  order  to  accelerate  its  reduction  or  decompo- 
sition by  heat.  Chloride  of  silver,  for  instance,  con- 
sists, as  we  have  seen,  of  metallic  silver,  combined  with 
the  gaseous  body  called  chlorine,  with  which  it  forms 
a  white  powder.  The  chlorine  being  very  firmly  com- 
bined with  the  silver,  can  only  be  separated  from  it 
by  adding  another  substance  for  which  it  has  a  still 
greater  attraction  or  affinity  than  for  the  silver.  The 
substance  usually  added  for  this  purpose  is  an  alkali, 
or  alkaline  carbonate  (soda  or  potash).  When  the 
chloride  of  silver  is  mixed  with  one  of  these  substan- 
ces and  exposed  to  a  red  heat,  the  chlorine  leaves  the 
silver  and  combines  with  the  alkali,  forming  the  chlo- 
ride of  potash  or  soda,  as  the  case  may  be,  and  liber- 
ating the  silver  in  the  uncombined  or  metallic  condi- 
tion. This  is  the  rationale  of  reduction.  The  princi- 
pal objects  of  fluxing  are  : 

1.  To  cause  the  more  ready  fusion  of  a  body,  which 
it  is  difficult  or  impossible  to  fuse  by  itself. 

2.  To  fuse  a  foreign  substance  mixed  with  a  metal, 
in  order  to  separate  the  latter  by  its  difference  of  spe- 
cific gravity. 


66 


THE  reducer's  MANUAL. 


3.  To  prevent  the  formation  of  alloys,  or  tlie  com- 
bination of  the  base  metals  with  the  precious  ones. 

4.  To  obtain  a  single  button  of  metal,  which  others 
wise  would  be  diffused  in  small  globules. 

The  largest  yields  in  reducing  are  obtained  by  first 
bringing  the  compound  to  be  reduced,  as  well  as  the 
flux,  to  the  finest  possible  powder  and  the  most  inti- 
mate mixture.  Already  from  the  earliest  times  the 
ingenuity  of  individuals  has  been  taxed  to  produce 
mills  or  crushers  for  grinding  the  ores  containing  gold 
and  silver  to  the  finest  possible  powder,  as  it  has  been 
abundantly  proved  that  this  result  is  necessary  to  pro- 
duce the  largest  yields  of  the  precious  metals.  All 
residues,  previous  to  fluxing,  should  be  pounded  to 
the  finest  powder,  in  a  large  iron  or  steel  mortar. 
The  proper  selection,  pro^Dortion  and  mixture  of  the 
fluxes  is  the  whole  secret  which  leads  to  the  most  suc- 
cessful reduction.  The  most  important  single  sub- 
stances used  as  flux  are  the  following: 

Borax  or  Biborate  of  Soda. 

An  excellent  and  almost  universal  flux,  because  it  has 
the  valuable  property  of  forming  fusible  compounds 
with  nearly  all  the  bases.  It  is  consequently  very  use- 
ful in  purifying  buttons  of  silver  or  gold,  combining 
with  and  extracting  the  base  metals,  and  rendering 
both  the  silver  and  gold  perfectly  pure.  To  prepare 
the  commercial  borax  as  a  flux,  it  must  be  freed  of  its 
water  of  crystalization,  which  is  best  done  by  half  fill- 
ing a  sand  crucible  with  the  borax  and  exposing  it  to 
heat  until  it  is  perfectly  liquid,  when  it  should  be 
poured  upon  a  large  plate  or  stone,  and,  when  cool, 


THE  BEDUCEr's  MANUAL. 


67 


broken  into  fragments  and  preserved  in  well  stoppered 
bottles. 

Carbonate  of  Potash  and  Carbonate  of  Soda 
possess  great  advantages  over  other  single  fluxes,  as 
they  are  very  efficient  oxidizers  and  de-sulphurizers, 
and  are  very  economical.  Carbonate  of  potash  is  much 
preferable  to  soda,  as  it  gives  a  very  liquid  and  easily 
flowing  glass,  at  a  comparatively  low  temperature.  On 
account  of  its  great  fusibility,  it  possesses  the  power 
of  holding  in  suspension  a  large  quantity  of  insoluble 
matter,  as  earth,  charcoal,  etc.,  etc.  Carbonate  of  soda 
has  an  advantage  over  potash  in  not  deliquescing  or 
absorbing  water  from  the  atmosphere,  and,  as  a  mix- 
ture of  the  two,  is  not  open  to  this  objection;  it  com- 
bines the  advantages  of  both.  The  best  proportion  is : 

Carbonate  of  potash  -       -       -    15  ounces. 

Carbonate  of  soda     -  -    10  " 

Nitrate  of  Potash. 
Nitrate  of  potash,  or  saltpeter,  is  used  very  exten- 
sively for  refining  and  purifying  gold  and  silver.  It 
has  a  great  tendency  to  oxidize,  and  consequently  to 
remove  the  common  metals.  This  gives  us  a  very  effi- 
cient method  of  rendering  gold  or  silver  perfectly 
pure;  it  is  quite  as  excellent  for  refining  as  borax,  and 
costs  but  one-half.  Saltpeter  is  likewise  very  useful, 
added  in  small  lumps,  to  burn  out  the  carbon  when 
reducing  the  paper  ashes,  which  tends  to  make  the 
flux  "  stiff." 

Common  Salt  {Chloride  of  Sodium). 
Common  salt  is  of  much  use  in  silver  reductions,  as 
it  checks,  to  a  great  extent,  the  tendency  of  the  fused 


68  THE  reducer's  manual. 

mass  to  boil  over,  and  renders  most  fluxes  much,  more 
easy  flowing  and  liquid. 

Black  Flux, 

Black  flux  is  both  a  fusing  and  reducing  agent.  It 
consists  of  a  very  intimate  mixture  of  carbonate  of  pot- 
ash and  charcoal.  It  is  a  very  useful  flux  for  chloride 
of  silver  and  many  other  substances.  To  prepare  it, 
mix  intimately: 

Cream  of  tartar  -      -      -      -    16  ounces. 

Saltpeter  8  " 

Place  the  mixture  upon  an  iron  pan  and  ignite  it 
with  a  red  hot  coal.  When  the  combustion  is  com- 
pleted, the  black  mass  must  be  powdered  and  sifted 
while  yet  hot,  and  placed  into  a  well  stoppered  bottle, 
as  it  rapidly  absorbs  moisture  from  the  air. 

Resin, 

A  most  excellent  flux  for  the  chloride  of  silver  is 
resin.  It  should  be  finely  powdered  and  mixed  inti- 
mately with  the  chloride  of  silver.  It  has  been  proved 
that  before  the  chloride  of  silver  attains  a  temperature 
sufficient  to  obtain  a  reduction,  small  portions  of  it  are 
volatilized.  By  fusing  with  resin  this  difficulty  is  en- 
tirely overcome. 

Molasses,  Soap  and  Sugar, 

These  form  excellent  fluxes  for  the  chloride  of  silver. 
Scrapings  or  raspings  of  Castile  soap  answer  the  pur- 
pose admirably. 

We  have  given  this  rather  lengthy  list  of  fluxes,  so 
that  after  a  little  experience  the  reader  may  be  able  to 
select  for  himself  the  substance,  or  combination  of  sub- 
stances, most  suited  to  his  convenience,  apparatus  and 


THE  reducer's  MANUAL. 


69 


facilities.  We  will  now  proceed  to  describe  the  metliod 
which  we  have  adopted  for  reducing  residues  and  know 
by  experience  to  give  good  results. 

FLUXING. 

Having  reduced  the  paper  clippings  and  filters  to 
ashes,  the  next  step  which  should  be  taken  is  to  sift 
them.  In  the  paper  wastes  of  photographic  establish- 
ments, there  is  always  a  large  amount  of  impurity, 
which  renders  the  flux  stiff  and  the  results  impure. 
The  ashes  should  be  rubbed  to  powder  and  thrown 
upon  a  fine  flour  sieve.  The  glass,  nails,  etc.,  may 
then  be  readily  picked  out.  The  residue  which  will 
not  pass  through  the  sieve,  should  be  thrown  into  a 
mortar  and  powdered  as  long  as  any  coarse  grains  re- 
main behind.  When  the  ashes  are  rich  in  silver, 
spangles  of  metallic  silver  are  frequently  left  upon  the 
sieve;  these  should  be  added  to  the  ashes.  Having 
concluded  this  operation,  the  following  flux  should  be 
prepared: 

Carbonate  of  potash  -       -      -    16  ounces. 

Carbonate  of  soda  -  -  -  4  " 
Mix  the  ashes  intimately  with  their  own  weight  of 
flux;  fill  a  Hessian  crucible  about  three-quarters  full, 
with  the  resulting  mass,  and  strew  a  thin  layer  of  salt 
upon  the  surface.  The  crucible  and  contents  are  now 
ready  for  the  fire. 

Developer  Washings. 

When  the  developer  drainings  have  been  prepared 
by  adding  a  solution  of  common  salt,  the  black  pow- 
der being  thoroughly  dried,  should  be  mixed  with  its 
weight  of  the  following  flux: 


70 


THE  BEDUCEE's  MANUAL. 


Carbonate  of  potash  -      -      -    10  ounces. 
Nitrate  of  potash      -       -       -  2 

It  should  be  placed  into  the  crucible,  precisely  like 
the  former.  This  flux  flows  easily,  gives  a  fine  glass 
and  takes  up  all  impurities. 

Collodion  Film  Ashes. 

The  ashes  of  the  collodion  films  consist  chiefly  of  io- 
dide and  bromide  of  silver  and  some  organic  matter. 
The  best  flux  for  the  reduction  of  these  wastes  is  the 
following  : 

Carbonate  of  potash  -      -      -     8  ounces. 
Carbonate  of  soda     -       -      -     1  ounce. 

Add  the  flux  in  the  proportion  of  five  ounces  of  the 
ashes  to  four  of  the  flux,  and  treat  as  the  last. 

Flux  for  Sulphide  of  Silver, 

The  sulphide  of  silver  is  the  most  difficult  of  the 
compounds  of  silver  to  reduce.  When  it  has  been  pre- 
viously roasted,  as  directed  on  page  49,  the  following 
flux,  mixed  in  proportion  of  fourteen  ounces  of  the  sul- 
phide to  sixteen  of  the  flux,  answers  excellently  : 

Flux  for  Roasted  Sulphide  of  Silver. 

Carbonate  of  potash  -      -      -    15  ounces. 
Carbonate  of  soda     -      -       -  10 

When  it  is  desirable  to  do  away  with  the  first  heat- 
ing, the  subjoined  formula  answers  very  well: 

Carbonate  of  potash  -      -      -   16  ounces. 
Iron  filings        -       -       -       -     2  " 

Mixed  in  proportion  as  the  last. 


THE  EEDUCEr's  MANUAL. 


71 


The  last  named  flux  requires  a  mucli  higher  heat 
than  the  former. 

A  flux  which  is  superior  to  all  others  for  the  re- 
duction of  sulphide  of  silver,  is  the  salt  obtained  by 
the  evaj3oration  of  the  waste  cyanide  fixing  solution, 
as  recommended  on  page  53.  To  every  sixteen  ounces 
of  the  sulphide  of  silver,  twelve  ounces  of  the  cyanide 
salt  should  be  added,  and  when  thoroughly  mixed 
together,  a  crucible  is  filled  with  the  black  mass.  In 
this  case  the  crucible  should  not  be  more  than  half 
full,  as  the  mixture  scathes  very  violently  when  ex- 
posed to  a  red  heat.  The  result  of  the  reduction  is 
pure  metallic  silver  and  sulpho-cyanide  of  potash. 
This  process  should  only  be  made  use  of  when  it  is 
not  desired  to  regain  the  cyanide  of  potash,  as  by 
these  means  a  still  larger  economy  is  obtained. 

The  Toning  Bath  Precipitate — How  to  Flux  it. 

The  precipitate  obtained  by  the  addition  of  sulphate 
of  iron  to  old  toning  baths  consists,  as  we  have  before 
stated,  of  metallic  gold,  mixed  with  a  large  amount  of 
iron  and  the  oxide  of  iron.  "When  but  a  small  amount 
of  the  precipitate  is  at  hand,  the  wet  method  of  treat- 
ing it  is  much  to  be  preferred  to  fusion.  If,  however, 
a  considerable  amount  of  this  class  of  residue  has  ac- 
cumulated, it  should  be  mixed  with  saltpeter  in  the 
following  proportions : 

Gold  precipitate       -      -       -    16  ounces. 
Saltpeter  -      -       -       -  12  to  14  " 

The  crucible  into  which  the  mixture  is  placed 
should  likewise  be  filled  but  half  full.    On  being  ex- 


72 


THE  reducer's  MANUAL. 


posed  to  a  bright  red  heat,  the  gold  is  obtained  in  a 
nearly  pure  condition,  the  iron  being  oxidized  and 
dissolved  by  the  saltpeter. 

Chloride  of  Silver, 

The  chloride  of  silver  obtained  by  the  precipitation 
of  old  baths,  from  the  washings  of  prints,  nitric  acid 
plate  cleaning  solution  and  cyanide  solution,  may  all, 
after  being  well  washed,  be  mixed  together  previous 
to  reduction.  The  chloride,  having  been  exposed  to  a 
brisk  heat,  in  order  to  expel  any  residuary  moisture, 
should  be  mixed  with  half  its  weight  of  the  following 
flux: 

Carbonate  of  potash         -      -   16  ounces. 
Powdered  resin         -       -      -     2  " 

The  crucible  may  be  tightly  packed  three-quarters 
full,  and  a  thin  layer  of  salt  strewn  upon  the  top. 

The  residues  having  been  fluxed  and  placed  in 
the  crucibles  in  the  manner  described,  are  now  ready 
for  reduction. 

REDUCTION. 

The  furnace  having  been  properly  set,  and  the  ne- 
cessary appendages  provided,  as  directed  on  page  38, 
a  piece  of  brick,  of  about  the  size  of  the  bottom  of  the 
crucible,  should  be  placed  in  the  middle  of  the  grate, 
so  that  it  does  not  obstruct  much  of  the  draft.  The 
crucible  is  set  firmly  upon  this  brick,  and  shavings 
and  thin  kindling-wood  filled  up  to  its  mouth  and  ig- 
nited. When  the  wood  is  thoroughly  ablaze,  charcoal, 
broken  into  the  size  of  a  large  walnut,  is  thrown  upon 


THE  reducer's  MANUAL. 


73 


it.  Tlie  crucible  may  now  be  covered,  and  the  coke, 
or  mixed  fuel,  filled  right  over  its  top. 

When  the  fuel  has  burned  away,  it  should  be  poked 
down  around  the  sides  of  the  crucible,  and  more  added 
as  quickly  as  it  is  required.  If,  when  the  contents  of 
the  crucible  is  liquid  and  thoroughly  fused,  any  of  the 
residue  is  left,  it  may  be  done  up  in  thin  paper,  in 
the  form  of  a  cartridge,  and  added  occasionally  until 
the  crucible  is  full;  or  the  residue  may  be  added  with 
an  iron  spoon  held  by  the  tongs.  Should,  upon  its  ad- 
dition the  fused  mass  boil  over,  it  may  be  quickly 
cooled  down  by  stirring  it  with  a  cool  poker  or  rod  of 
iron. 

When  the  last  portion  of  the  residue  has  been 
added,  the  fire  should  be  raked,  fresh  fuel  added,  and 
the  heat  allowed  to  reach  its  highest  intensity.  After  * 
about  thirty  minutes'  time,  the  reduction  will  be  com- 
plete. To  ascertain  this  to  a  certainty,  lift  off  the 
cover  of  the  crucible,  and  if  the  fused  mass  answers  to 
the  following  tests  the  operation  is  completed: 

1.  The  mass  must  be  perfectly  liquid  and  almost  at 
a  white  heat. 

2.  When  stirred  with  an  iron  wire  it  must  feel 
liquid,  and  not  as  if  full  of  sand  or  grit. 

3.  When  a  cool  iron  is  plunged  into  the  liquid  mass 
and  withdrawn,  an  even  or  smooth  black  glass  or 
slag  must  be  formed  upon  it,  not  one  rough  or 
sandy. 

4.  On  dipping  an  iron  wire  to  the  bottom  of  the 
crucible,  the  fused  silver  can  be  felt  by  its  resistance, 
and  by  a  bubbling  or  rumbling  feeling  in  the  rod  or 
wire. 


THE  EEDUCEk's  MANUAL. 


If  the  fused  mass  does  not  answer  tliese  tests, 
th  cover  should  be  replaced  upon  the  crucible  and  the 
heat  again  allowed  to  reach  its  maximum. 

"Where  the  contents  of  the  crucible  answer  all  these 
tests  the  pot  may  be  removed  from  the  fire  and  al- 
lowed to  cool,  or  the  contents  may  be  poured  into  an 
iron  mortar  greased  with  a  little  lard  or  tallow.  A 
crucible,  when  of  a  good  quality,  may  be  used  twice, 
or  even  three  times,  with  safety. 

We  have  thus  given  the  chief  directions  necessary, 
but  there  are  of  course  still  many  little  points  and 
knacks  which  it  would  be  impossible  to  describe,  and 
which  can  only  be  gained  by  experience  and  practice. 
There  are  also  many  little  precautions  necessary  in 
order  to  avoid  loss  of  silver.  Thus  the  coke  or  mixed 
fuel  should  be  always  plentifully  supplied,  and  packed 
down  around  the  crucible  as  quick  as  it  becomes  con- 
sumed, as  if  a  current  of  cold  air  strikes  the  crucible 
while  red  hot,  it  is  ahnost  sure  to  crack  it;  then  again, 
in  poking  the  coals  around  the  pot,  it  is  very  liable  to 
crack,  or  when  the  residue  contains  much  iron,  it 
burns  a  hole  right  through  inferior  crucibles. 

In  adding  the  residue  in  wads,  care  is  also  neces- 
sary, as  the  fused  mass,  especially  if  at  a  high  tempera- 
ture, readily  boils  over,  or  loss  may  be  occasioned  by 
not  adding  the  residue  carefully  or  allowing  the  paper 
wad  to  catch  fire  before  it  reached  the  crucible.  All 
these  and  many  other  little  points  are  necessary  to  in- 
sure the  largest  yields,  but  they  are  readily  learnt  by  a 
little  practice.  When  the  melted  mass  is  not  poured 
into  a  mold,  but  is  allowed  to  cool  in  the  pot,  the  cru- 
cible should  be  gently  tapped  with  a  piece  of  wood,  so 


THE  KEDUCER's  MANUAL. 


75 


that  any  globules  of  silver  retained  or  diffused  in  the 
glass  or  flux,  may  be  separated  or  forced  to  the  bot- 
tom. It  must  then  be  left  undisturbed  to  cool.  When 
perfectly  cold  it  must  be  broken  open  with  a  hammer 
and  the  gold  or  silver  will  be  found  at  the  bottom,  in 
the  form  of  a  lump  or  button. 

If  the  reduction  has  been  well  performed  the  silver 
is  obtained  in  one  lump,  and  no  globules  of  silver 
would  be  found  diffused  through  the  flux,  while  di- 
rectly the  contrary  is  the  case  if  the  operation  has  not 
been  properly  conducted.  When  paper  ashes  are  re- 
duced, the  flux  is  very  liable  toiibecome  stiff  or  thick; 
it  is  then  advantageous  to  throw  upon  the  redhot  mass 
a  lump  of  saltpeter  of  the  size  of  a  filbert.  By  these 
means  some  of  the  impurities  are  burnt  out. 

REFININa,  PURIFICATION  AND  GRANULATION. 

Only  the  silver  obtained  from  the  chloride  can  be 
considered  perfectly  pure ;  that  obtained  from  the  sul- 
phide ashes,  or  developer  drainings,  being  always  more 
or  less  contaminated  with  iron,  or  other  impurities. 
If  intended  for  the  production  of  nitrate  of  silver, 
purity  is  indispensible,  while  if  the  metal  is  to  be  sold, 
it  always  brings  a  much  higher  price.  The  impure 
silver,  as  obtained  from  the  residues,  is  placed  in  a 
melting-pot  and  brought  to  thorough  fusion.  Salt- 
peter, in  small  lumps,  should  then  be  thrown  upon  the 
redhot  mass,  in  about  the  following  proportion: 

Metallic  silver   -       -       -       -     8  ounces. 
Saltpeter.  -----     1  ounce. 

When  the  violent  deflagration  ensuing  has  ceased, 


76 


THE  reducer's  MANUAL. 


the  heat  should  be  kept  at  its  greatest  intensity  for 
fifteen  or  twenty  minutes  longer.  The  crucible  is 
then  removed  from  the  fire,  and  its  contents  quickly 
and  dexterously  poured  into  an  iron  mold;  or  the  pot 
may  be  allowed  to  cool,  and  finally  broken  open  with  a 
hammer.  The  button  of  silver  thus  obtained,  after 
being  thoroughly  cleaned  from  all  adhering  flux  (if 
intended  for  the  manufacture  of  nitrate  of  silver), 
must  be  granulated.  For  this  purpose  place  the  pure 
buttons  of  silver,  obtained  as  last  described,  into  a  clean 
crucible,  without  flux,  and  expose  to  an  intense  heat. 
When  thoroughly  melted,  remove  the  pot  from  the  fire, 
and  slowly,  but  steadily,  pour  its  contents  into  a  pail  of 
water,  from  the  height  of  three  or  four  feet.  In  pour- 
ing the  silver  into  the  water,  the  crucible  should  be 
gently  swayed  from  side  to  side,  so  that  the  globules 
of  the  melted  metal  may  be  more  thoroughly  sepa- 
rated. The  spangles  of  silver  thus  obtained  should  be 
carefully  dried  and  kept  in  a  clean  stoppered  bottle  for 
future  use.  The  process  of  granulation  is  only  neces- 
sary when  the  silver  is  to  be  used  for  chemical  pur- 
poses. It  should  always  be  sold  in  the  form  of  a  bar  or 
button. 

If  the  metallic  silver  has  a  bright  and  clean  appear- 
ance, and  is  free  from  all  adhering  flux,  it  always 
fetches  a  higher  price  than  the  purest  silver  in  a  less 
attractive  form.  To  obtain  the  silver  as  a  bright  but- 
ton, the  fused  mass  should  be  allowed  to  cool  com- 
pletely before  any  attempt  is  made  to  knock  off  the  ad- 
hering flux.  The  button  may  be  further  cleaned  and 
brightened  by  placing  it,  when  cold,  into  the  fpllowing 
solution: 


THE  EEDUCER's  MANUAL. 


77 


Chemically  pure  hydrochloric  acid  16  ounces. 
Water       -      -      -      -      -     4  " 

Or  it  may  be  boiled  in  a  solution  consisting  of : 
Bitartarate  of  potash  (cream  of 

tartar)  8  ounces. 

Water  18  " 

When  the  desired  result  has  been  obtained,  the  but- 
ton should  be  wiped  dry  with  a  cloth,  or  it  may  be 
further  improved  by  scouring  with  fine  emery  or  sand 
mixed  with  a  little  water.  What  we  have  said  of  silver 
applies  equally  well  to  gold. 

PRACTICAL  SUGGESTIONS. 

Old  or  cracked  crucibles  may  be  used  with  much 
success  as  stands  or  supports  of  the  melting  pot  in  the 
furnace.  It  is  superior  to  a  brick  placed  upon  the 
grate,  as,  being  very  thin,  they  are  very  quickly  heated 
through,  and  tend  to  equalize  and  distribute  the  heat 
around  the  crucible  containing  the  residue.  In  remov- 
ing the  crucible  from  the  fire,  the  hand  should  be  pro- 
tected by  a  pair  of  buckskin  gloves,  so  that  the  strength 
of  the  grip  may  not  be  diminished  by  the  intense  heat. 
The  operator  should  never  omit,  after  having  removed 
the  pot  from  the  fire,  to  thump  the  sides  of  the  cru- 
cible, especially  if  the  flux  be  stiff,  as  by  these  means 
any  stray  globules  of  silver  are  caused  to  run  together. 
As  a  mold,  a  small  iron  crucible  is  the  most  convenient 
vessel.  It  should  be  previously  heated,  so  that  it  can- 
not be  touched  by  the  hand,  and  lightly  greased  inside 
with  a  little  lard  or  tallow.  If  an  iron  mortar  is  not 
at  hand,  a  small  vessel  may  be  bent  out  of  heavy  sheet 
iron,  which  answers  the  purpose  perfectly  well. 


78 


THE  KEDUCEB's  MANUAL, 


A  small  stock  of  tlie  fluxes  should  always  be  kept  on 
hand,  in  well  stoppered  bottles,  so  that  they  can  ab- 
sorb no  particle  of  moisture. 

Considerable  skill  is  requisite  to  produce  well  gran- 
ulated silver.  A  very  excellent  method  is  to  pour  the 
melted  metal  through  a  hroom^  as  by  these  means  the 
particles  of  silver  are  separated  and  a  finer  division  of 
the  metal  is  insured. 

We  append  a  list  of  the  most  esteemed  fluxes,  from 
which  the  reader  may  select  the  one  best  adapted  to 
his  requirement. 

rOEMULAS  FOR  FLUXES,  ETC.,  ETC. 

For  Ashes. 
No.  1. 

Carbonate  of  potash  -      -      -   24  ounces. 
Carbonate  of  soda     -      -      -     6  " 
Common  salt    -      -      -      -     2  " 
To  be  mixed  with  the  ashes,  weight  for  weight. 
No.  2. 

Carbonate  of  potash  -      -      -   20  ounces. 
Carbonate  of  soda     -      -      -    18  " 
Common  salt     -      -      -      -     8  " 
Fourteen  ounces  of  the  flux  to  be  added  to  sixteen 
of  the  ashes.  Eequires  a  higher  heat  than  the  former. 

No.  3. 

Carbonate  of  potash  -      -      -   15  ounces. 
Silver  ashes      -      -      -      -    16  " 
Answers  every  requirement  of  a  good  flux. 
No.  4. 

Carbonate  of  potash  -      -      -     8  ounces. 
Nitrate  of  potash      -      -      -     4  " 


THE  REDUCEB's  MANUAL. 


79 


Benders  the  result  pure  by  removing  the  iron,  ad- 
ded weight  for  weight. 

No.  5. 

Carbonate  of  potash  -      -      -     8  ounces. 
Carbonate  of  soda     -      -      -     8  " 
Fused  borax     -      -      -      -  8 
One  pound  of  this  flux  is  sufficient  for  every  pound 
of  ashes. 

No.  6. 

Caustic  potash  -      -      -      -    16  ounces. 

Silver  ashes      -       -       -       -    16  " 
A  very  excellent  flux,  if  used  immediately ;  but  ab- 
sorbs moisture  and  becomes  liquid  in  a  very  short 
time. 

For  Developer  Washings^  Prepared  by  First  Method. 
No.  1. 

Nitrate  of  potash      -      -      -     8  ounces. 
Carbonate  of  potash  -      -      -     2  " 
Add  three-quarters  of  a  pound  to  every  sixteen 
ounces  of  dried  precipitate. 

No.  2. 

Nitrate  of  potash      -      -      -     8  ounces. 
Carbonate  of  potash  -       -       -     8  " 
Carbonate  of  soda     -      -      -  4 
In  proportion  same  as  last. 

No.  3. 

Nitrate  of  potash      -      -      -   10  ounces. 
Dried  precipitate      -      -      -    12  " 
No.  4. 

Borax  16  ounces. 

Carbonate  of  potash  -      -      -     4  " 


80 


THE  reducer's  MANUAL. 


Added  -weiglit  for  weigM.  Inferior  to  the  preced- 
ing formula. 

No.  5. 

Carbonate  of  soda     -       -      -    14  ounces. 
Cyanide  of  potash     -       -      -     4  " 

Very  good,  but  expensive.  Twelve  ounces  of  flux  to 
each  pound  of  residue. 

For  Old  Collodion  Films,  etc.,  etc. 

No.  1. 

Nitrate  of  potash      -      -      -     4  ounces. 
Carbonate  of  potash  -      -      -     2  " 
Half  as  much  flux  as  ashes. 

No.  2. 

Caustic  potash  -      -      -      -     4  ounces. 
Caustic  soda     -       -       -      -     2  " 
Nitrate  of  potash      -      -      -     1  ounce. 
In  proportion  same  as  last.    Is  a  superb  flux,  but 

absorbs  moisture  almost  instantaneosly  when  exposed 

to  the  air. 

No.  3. 

Carbonate  of  potash  -      -      -     4  ounces. 
Borax       -----     4  « 

Added  to  the  ashes  in  the  proportion  of  twelve 
ounces  of  residue  to  ten  ounces  of  flux. 

No.  4. 

Caustic  potash  -      -      -      -     8  ounces. 
Nitrate  of  potash      -      -      -  8 
Half  a  pound  of  flux  to  even  pound  of  ashes. 
No.  5. 

Carbonate  of  potash  -      -      -     8  ounces. 
Cyanide  of  potash     -      -      -     2  " 


THE  EEDUCERS  MANUAL. 


81 


Mixed  in  proportion  same  as  last.  Flows  easy  and 
renders  the  result  pure  by  oxidation. 

For  Cfdoride  of  Silver, 

No.  1. 

Carbonate  of  potash  -      -  - 
Powdered  resin  - 

Add  half  the  weight  of  the  chloride 

No.  2. 

Carbonate  of  potash  -  -  - 
Chloride  of  silver      -      -  - 

No.  3. 

Chloride  of  silver  -  -  - 
Eesin  

No.  4. 

Carbonate  of  potash  -  -  - 
Carbonate  of  soda     -       -  - 

Proportion  the  same  as  the  first. 

No.  5. 


Caustic  potash  - 
Chloride  of  silver 


Chloride  of  silver 
Black  flux 


No.  6. 


No.  7. 


Carbonate  of  potash 
Bitartarate  of  potash 
Chloride  of  silver 


16  ounces. 
2  " 


8  ounces. 
16  " 

8  ounces. 
12  " 

8  ounces. 
4 


8  ounces. 
16  " 


4  ounces. 
3  " 


4  ounces. 
2  " 
8  " 


82 


THE  KEDUCEE'S  MANUAL. 


For  Toning  Bath  Precipitate. 
No.  1. 

Nitrate  of  potash      -      -      -     8  ounces. 
Carbonate  of  soda     -      -       -     4  " 
Added  to  the  residue  weight  for  weight. 

No.  2. 

Nitrate  of  soda        -      -      -     8  ounces. 
Eesidue    -----     4  « 
No.  3. 

Nitrate  of  potash     -      -      -     8  ounces. 
Carbonate  of  potagh  -      -      -     4  " 
Eesidue  7  " 

For  Sulphide  of  Silver. 

No.  1. 

Carbonate  of  potash         -      -     8  ounces. 
Carbonate  of  soda     -       -       -     8  " 
Slacked  (well-dried)  lime  -       -     4  " 
This  flux  should  be  added,  weight  for  weight,  or 
even  a  considerable  increase  of  this  proportion  may- 
be made  use  of.    The  formula  given  above  is  very  ex- 
cellent, but  the  mixture  requires  a  high  heat. 

No.  2. 

Caustic  potash  -      -  -     8  ounces. 

Carbonate  of  soda     -       -      -     4  " 
Mixed  with  the  residue  weight  for  weight,  flows 
easy  at  a  low  temperature. 

No.  3. 

Carbonate  of  potash         -      -     8  ounces. 
Cyanide  of  potash    -      -      -     2  " 
Caustic  soda     -      -      -  ,      -     4  " 
Very  excellent,  though  rather  expensive. 


THE  REDUCEE's  MAUUAL* 


83 


No.  4. 


OE, 


Carbonate  of  potash 
Iron  filings 

Carbonate  of  potash  - 
Iron  filings 
Caustic  soda 
Proportion  same  as  last. 

No. 

Carbonate  of  potash 
Iron  filings 
Saltpeter  - 
Very  excellent. 


8  ounces, 

1  ounce. 

12  ounces. 

2  " 
4  " 


16  ounces. 

2i 


No.  6. 

The  cyanide  salt  obtained  by  the  eyaporation  of  the 
cyanide  fixing  solution,  mixed  with  four  ounces  of 
caustic  potash  to  each  pound  of  the  salt. 

This  is  one  of  the  best  known  fluxes  for  the  sulphide 
of  silver.  It  flows  easy  and  may  be  added  to  the  un- 
roasted  sulphide. 

Though  the  foregoing  enumeration  of  fluxes  may 
seem  unnecessarily  extended,  still  popular  taste  is  so 
varied  that  where  one  suits,  three  may  be  rejected. 
"We,  for  our  part,  see  no  necessity  of  making  compli- 
cated mixtures  of  diverse  substances,  but  prefer  and 
make  use  of  the  plain  carbonate  of  potash  for  all  and 
every  residue.  The  amount  of  potash  added  is  varied 
according  to  the  composition  and  nature  of  the  wastes. 
For  paper  ashes,  one  and  a  half  pounds  potash  to 
every  pound  of  ashes  may  be  mixed  together;  for  chlo- 
ride of  silver,  one-half  its  weight  of  potash,  etc.,  etc. 


CHAPTEE  VI. 


REDUCTIONS  BY  THE  WET  OB  GALVANIC  PEOCESS. 

Though  it  is  true  there  are  few  residues  whicli  can 
be  advantageously  reduced  by  the  wet  method,  yet  the 
processes  we  are  about  to  describe  are  so  simple  and 
economical,  that  the  practical  photographic  operator 
and  others  who  can  devote  little  time  and  attention  to 
this  subject,  will  find  these  methods  of  reduction  better 
adapted  to  their  wants  than  the  fire  reduction.  This 
is  especially  the  case  if  the  silver  regained  is  tq  be  used 
for  chemical  purposes,  as  by  these  means  the  metal  op- 
erated upon  is  always  obtained  in  a  state  of  extremely 
fine  mechanical  division — a  form  peculiarly  favorable 
to  chemical  action.  Were  it  not  that  the  wet  proces- 
ses are  limited  to  certain  compounds,  they  would  en- 
tirely supersede  the  fine  reductions  for  manufacturing 
purposes. 

In  this  chapter  we  purpose  to  give  the  best  methods 
for  the  reduction  of  residues  without  the  use  of  fire. 
Eeduction,  strictly  speaking,  is  the  transmutation  of 
a  metallic  compound  to  the  metal  itself;  but  under 
this  head  we  have  included  the  processes  for  regaining 
the  silver  in  a  useful  form  by  merely  chemical  means, 
and  without  reducing  them  to  the  metallic  state.  We 
can,  consequently,  divide  these  processes  into  two 
classes  :  1st.  Those  processes  based  entirely  upon 
chemical  action,  and  in  which  the  metal  contained  in 


THE  reducer's  MANUAL. 


85 


the  residue  is  converted  into  a  useful  compound.  2d. 
Those  dependent  upon  chemical  action  and  electricity 
or  galvanism,  in  which  case  the  metal  is  obtained  in  a 
metallic  or  uncombined  condition. 

In  the  first  case,  the  operation  consists  simply  in 
pouring  upon,  or  digesting,  the  gold  and  silver  resi- 
dues in  some  solution  which  has  the  power  of  combin- 
ing with  the  precious  metal  itself,  or  the  substance 
with  which  it  is  combined,  thus  altering  and  modifying 
its  chemical  properties.  In  the  second  case,  namely, 
by  the  action  of  electricity,  the  metal,  as  before  stated, 
is  obtained  in  the  metallic  condition,  while  the  solvent 
action  of  the  chemical  added  is  confined  to  the  sub- 
stance used  to  generate  this  electricity. 

TREATMENT  OF  WASTES  BY  CHEMICAL  ACTION. 

Paper  Clippings,  Filters,  Filtering  Cotton,  etc,  etc. 

For  successfully  treating  this  class  of  wastes  by  the 
wet  method,  a  thorough  combustion  of  the  paper  is  of 
primary  importance.  For  this  purpose  proceed  as 
directed  on  page  46.  "When  the  ashes  have  cooled 
they  must  be  carefully  sifted  through  a  fine  flour  sieve, 
and  all  impurities  removed,  while  the  globules  and 
spangles  of  metallic  silver  remaining  in  the  sieve  are 
added  to  the  sifted  mass.  Place  the  gray  powder  thus 
obtained  ,into  a  spacious  porcelain  evaporating  dish, 
and  for  each  pound  add  twenty-four  ounces  of  the  fol- 
lowing mixture : 

Pure  concentrated  nitric  acid    -    16  ounces. 
DistiUed  water  -       -       -       -     6  " 

and,  after  stirring  thoroughly  vnth  a  glass  rod,  set  the 
4 


86 


THE  reducer's  MANUAL. 


dish  and  contents  in  a  vessel  of  hot  water,  or  upon  a 
moderately  warm  stove.  After  the  violent  ebullition 
and  all  red  vapors  have  ceased,  bring  the  liquid  to  the 
boiling  point  and  let  it  simmer  about  fifteen  minutes; 
then  dilute  the  dark  muddy  mass  with  an  equal  bulk 
of  distilled  water,  throw  the  whole  contents  of  the  dish 
upon  a  large  paper  filter,  and  carefully  collect  the  clear 
liquid  trickling  through.  If  the  filtrate  still  looks  a 
little  murky  or  unclear  the  filtration  may  be  repeated. 
Wash  the  residue  remaining  with  a  little  distilled 
water,  and  add  this  filtrate  to  the  other.  The  solution 
thus  obtained  consists  of  moderately  pure  nitrate  of 
silver.  It  should  b  placed  in  a  porcelain  evaporating 
dish  and  boiled  to  dryness  on  a  sand  bath.  When  all 
of  the  water  has  evaporated  the  heat  should  be  still 
continued,  until  the  mass  of  white  crystals  (under  con- 
stant stirring)  begin  to  assume  a  dirty  brown  color, 
and  have  fused  to  a  dirty  colored  pasty  mass.  When 
this  stage  is  arrived  at,  quickly  remove  the  dish  from 
the  fire  and  allow  it  to  cool  perfectly;  then  add  enough 
distilled  water  to  effect  a  complete  solution,  or  until 
by  means  of  a  hydrometer,  you  have  brought  it  to  tjie 
strength  desired  for  your  bath,  and  filter  the  murky 
liquid  until  it  is  perfectly  clear.  By  these  means  a 
superb  and  perfectly  neutral  silver  bath  may  be  ob- 
tained. The  black  mass  remaining  in  the  filter  still 
contains  some  silver,  and  may  be  dried  and  reduced  or 
sold  at  the  option  of  the  operator.  This  process  has 
been  described  in  "  Humphrey's  Journal  of  Photo- 
graphy" by  a  gentleman  who  forgot  to  credit  its 
origin  to  the  author.  If  we  have  urged  the  necessity  of 
keeping  the  residues  clean  for  fire  reductions,  we  must 


THE  EEDUCEr's  MANUAL.  87 

urge  it  in  a  tenfold  degree  if  tliey  are  to  be  reduced 
by  the  wet  method.  If  the  paper  is  carefully  kept  and 
well  burnt,  the  resulting  silver  is  of  a  very  fair  purity; 
while  if  it  contains  nails,  pins,  or  similar  substances, 
the  nitrate  will  of  course  contain  a  variable  amount  of 
the  nitrates  of  iron,  copper,  etc.,  etc.,  substances  highly 
detrimental  to  a  good  bath  for  sensitizing  photographic 
plates.  But  with  a  little  careful  management  the  paper 
can  as  well  be  kept  perfectly  clean  as  mixed  with  for- 
eign substances. 

Treatment  of  Developer  Drainings. 

Place  the  precipitate  obtained,  as  directed  on  page 
48,  with  common  salt  (that  obtained  with  sulphide  of 
potash  will  not  answer)  upon  an  iron  shovel;  set  it 
upon  a  lively  coal  fire,  and  expose  it  to  a  red  heat  for 
about  fifteen  minutes.  "When  the  now  brick  red  pow- 
der has  cooled,  place  it  in  a  capacious  evaporating 
dish,  and  for  every  ounce  of  the  powder  add  an  ounce 
of  pure  hydrochloric  acid,  previously  diluted  with  half 
an  ounce  of  water,  and,  after  stirring  the  mixture,  place 
it  upon  a  stove  and  allow  it  to  gain  the  boiling  tem- 
perature. When  all  violent  effervescence  has  ceased, 
add  a  little  more  acid,  and  if  no  further  action  takes 
place  the  operation  is  complete.  Dilute  the  dark  liquid 
copiously  with  water  and  allow  the  black  precipitate  to 
settle.  Pour  or  decant  off  the  yellowish  green  solution 
(which  consists  of  the  chloride  of  iron,  and  is  of  no 
value  whatever) ;  throw  the  black  precipitate  upon  a 
filter,  and,  after  washing  copiously  both  with  hot  and 
cold  water,  allow  it  to  dry;  it  consists  of  nearly  pure 
metallic  silver.   This  may  be  made  into  the  nitrate,  as 


88 


THE  REDUCEb's  MANUAL. 


directed  in  another  chapter.  The  heating  of  the  pow- 
der may  be  dispensed  with,  but  more  acid  is  then  re- 
quired for  the  solution  of  the  iron  and  the  results  are 
never  so  reliable.  The  hydrochloric  acid  used  in  this 
process  need  not  be  chemically  pure,  and,  if  very  con- 
centrated, should  be  mixed  with  an  equal  bulk  of 
water;  but  if  only  moderately  strong,  not  more  than 
half  its  bulk  of  water  need  be  added.  This  process  is 
not  always  reliable,  and  we  would  thereupon  prefer 
the  fire  reduction.  If,  for  instance,  the  acid  is  too 
strong,  some  of  the  metallic  silver  is  changed  to  the 
chloride;  if  too  weak,  some  iron  remains  behind. 

Chloride  of  Silver — How  to  Change  it  into  Nitrate. 

To  change  the  chloride  into  the  nitrate  of  silver  is  a 
very  simple  and  economical  process,  to  perform  which 
proceed  as  follows: 

Place  recently  precipitated  chloride  of  silver  into  a 
large  glass  flask,  and  to  each  ounce  add  two  ounces  of 
a  concentrated  solution  of  caustic  potash;  set  the  flask 
upon  a  sand  bath  until  the  solution  begins  to  boil.  A 
marked  change  will  now  be  observed,  the  white  chlo- 
ride of  silver  will  rapidly  change  to  a  dark  brown,  and 
when  no  further  darkening  takes  place,  remove  the 
flask  and  dilute  its  contents  with  plenty  of  water.  Col- 
lect, wash  and  dry  the  dark  brown  powder  and  pre- 
serve in  well  stoppered  bottles.  It  consists  of  chemi- 
cally pure  oxide  of  silver,  and  may  be  used  either  for 
the  manufacture  of  nitrate  of  silver,  or,  if  only  small 
quantities  have  been  obtained,  for  neutralizing  and  re- 
storing acid  silver  baths. 

Another  method  which  answers  tolerably  well,  is  to 


THE  reducer's  MANUAL. 


89 


pour  upon  the  cliloride  a  concentrated  hot  solution  of 
carbonate  of  potash  and  boiling  the  mixture  as  before. 
The  resulting  brownish  powder  should  be  treated  pre- 
cisely like  the  former.  It  consists  in  this  case  of  car- 
bonate of  silver.  In  both  these  processes  it  is  abso- 
lutely indispensable,  that  the  chloride  of  silver  be 
freshly  precipitated,  or  at  least  not  allowed  to  dry; 
this  may  be  easily  accomplished  by  immersing  the 
precipitate  in  water,  and  keeping  it  submerged  until 
enough  has  accumulated.  (See  page  55.)  Care  should 
also  be  taken  to  keep  the  chloride  of  silver  perfectly 
clean.  The  nitrate  of  silver  solutions  to  be  precipi- 
tated should  be  previously  filtered  perfectly  clear,  the 
bottle  used  as  receptacle  be  properly  cleaned  and  always 
kept  corked  in  a  dark  corner  of  the  sensitizing-room. 
When  these  precautions  are  observed  the  results,  espe- 
cially of  the  first  process,  are  chemically  pure,  and  the 
resulting  nitrate  of  silver  is  consequently  of  a  very 
superior  quality. 

To  Change  Iodide  or  Bromide  of  Silver  into  the  Nitrate. 

A  process  very  similar  to  the  former.  Place  the 
recently  precipitated,  and  of  course  still  wet  mass,  into 
a  flask,  and  upon  each  ounce  pour  two  ounces  of  a  hot 
and  very  concentrated  solution  of  caustic  potash. 
Place  the  flask  and  contents  upon  a  sand  bath,  and  al- 
low the  liquid  to  boil  for  about  half  an  hour,  adding  a 
little  water  if  the  solution  boils  away  too  rapidly.  At 
the  end  of  this  time  dilute  the  contents  of  the  flask 
with  abundance  of  water;  decant  the  liquid  and  filter 
off,  and  wash  the  precipitate  thoroughly. 

The  result  is  also  oxide  of  silver.    "We  consider  this 


90 


THE  BEDUCEb's  MANUAL. 


process  rather  uncertain,  but  liave  often  obtained  good 
results  with.  it.  The  iodide  and  bromide  of  silver  is 
of  such  rare  occurrence,  however,  as  a  residue,  that 
the  process  is  of  no  practical  value. 

To  Change  the  Print  Washings  into  Nitrate  of  Silver. 

The  print  washings  consist  when  precipitated,  as  we 
have  seen,  of  pretty  pure  chloride  of  silver,  and  may 
consequently  be  treated  in  precisely  the  same  manner; 
more  care  is  however  necessary  to  keep  washings  clean 
as  slips  of  paper,  chips  of  wood,  etc.,  etc.,  all  tend  to 
make  the  results  impure.  The  barrel  or  jar  containing 
this  residue,  should  be  kept  well  covered  over  from 
dust,  etc. 

How  to  Treat  the  Toning  Bath  Residue. 
The  precipitate  of  the  toning  bath  obtained,  as  di- 
rected on  page  54,  by  the  addition  of  a  solution  of  sul- 
phate of  iron,  can  be  much  more  advantageously  re- 
duced by  the  wet  method  than  by  fire,  especially  as 
there  can  be  but  little  collected  even  in  the  largest 
galleries. 

When  the  ebony  black  powder  has  been  dried,  place 
it  upon  a  shovel  or  other  iron  vessel,  and  expose  it  to 
a  red  heat  on  a  coal  fire  for  at  least  ten  minutes.  The 
contents  of  the  shovel  will  now  be  found  to  have 
changed  from  jet  black  to  dark  red,  owing  to  the  liber- 
ation of  sesquioxide  of  iron.  Place  this  red  powder  in 
an  evaporating  dish,  or  a  large  flask,  and  pour  upon  it 
the  following  mixture  (three  or  four  ounces  of  acid  to 
one  of  precipitate) : 

Strong  hydrochloric  acid  -      -     8  ounces. 

Water  6  " 


THE  reducer's  MANUAL. 


91 


Place  the  dish  upon  a  stove  and  heat  it  until  all 
effervescence  has  ceased  and  the  liquid  begins  to  boil; 
then  dilute  with  plenty  of  water,  and  filter,  wash  and 
dry  the  black  powder,  which  consists  of  pure  metallic 
gold  in  a  state  of  minute  division.  The  gold  must  be 
washed  very  thoroughly  while  upon  the  filter  (both 
with  hot  and  cold  water),  to  ensure  the  removal  of  the 
chloride  of  iron  formed.  The  acid  used  need  not  be 
chemically  pure,  but  care  should  be  taken  that  it  con- 
tains no  free  chlorine,  as  this  would  dissolve  the  gold 
and  cause  a  considerable  loss.  To  test  acid  as  to  its 
containing  free  chlorine,  proceed  as  follows : 

Place  a  few  drops  of  the  acid  upon  a  watch-glass, 
and  lay  in  these  a  minute  piece  of  real  gold  leaf.  If 
the  gold  leaf  disappears,  the  acid  should  be  rejected; 
while  if  it  remains  in  the  liquid  without  being  dis- 
solved, the  acid  may  be  used.  Or  the  following  mix- 
ture may  be  made  use  of,  though  it  is  much  inferior  to 
the  former: 

Sulphuric  acid  -       -       -       -     8  ounces. 
Water  16  " 

Three  or  four  ounces  of  acid  should  be  added  to 
each  ounce  of  precipitate,  and  the  mixture  treated  pre- 
cisely like  the  former. 

Old  Solutions  of  Nitrate  of  Silver,  etc.,  etc. 

When  a  bath  is  rejected,  and  is  no  longer  reliable  in 
its  action,  it  should  be  placed  in  a  large  flask  or  other 
suitable  vessel,  and  the  following  solution  added  as 
long  as  it  causes  a  precipitate : 

Carbonate  of  soda     -      -      -     8  ounces. 

Water  12  " 


92 


THE  reducer's  MANUAL. 


OR, 

Caustic  potash  -      -      -      -     4  ounces. 
Water  12  " 

Then  add  water,  wash  the  precipitate  thoroughly  and 
abundantly  with  warm  water,  and  finally  dry  and  pre- 
serve it  in  well  stoppered  bottles.  The  first  precipi- 
tate consists  of  carbonate  of  silver,  the  second  of  oxide 
of  silver. 

A  solution  of  lime  is  also  a  very  excellent  precipitat- 
ing solution  for  silver.  Place  some  lumps  of  lime  in  a 
wide  mouthed  bottle  and  add  considerable  water;  al- 
low the  mixture  to  remain  at  rest  for  several  days,  and 
then  drain  off  the  clear  liquid  that  has  gathered  on 
the  top.  This  solution  possesses  many  advantages 
over  potash  or  soda. 

REDUCTION  OF  SILVER  COMPOUNDS  TO  THE  METALLIC  STATE 
BY  GALVANIC  ACTION. 

When  soluble  metallic  salts  are  treated  with  chemi- 
cals that  generate  electricity,  or  are  exposed  to  a  cur- 
rent from  a  battery,  they  are  invariably  decomposed 
and  changed  to  the  metallic  condition.  This  decom- 
posing and  reducing  action  of  galvanic  or  voltaic  elec- 
tricity, aflfords  us  a  convenient  and  efficient  method  of 
utilizing  or  regaining  the  silver  from  waste  silver  solu- 
tions; but  its  application  is  also  limited  to  a  few  com- 
pounds, and  here,  as  in  the  foregoing  processes,  sul- 
phide of  silver  is  the  most  obstinate,  and  the  chloride 
the  most  tractable. 

There  are  several  methods  for  successfully  treating 
the  chloride  of  silver  by  galvanic  action,  and  we  will 
proceed  to  describe  the  simplest  of  these. 


THE  reducer's  MANUAL. 


93 


1.  Place  recently  precipitated  or  still  wet  chloride 
of  silver  in  a  porcelain  evaporating  dish,  in  a  cup,  flask 
or  any  other  convenient  vessel,  and  mix  with  it  half  its 
weight  of  small  pieces  of  zinc.  Then  add  enough  of 
the  following  solution,  to  cause  a  very  lively  efferves- 
cence, and  let  the  mixture  stand  over  for  a  day  or  so : 

Sulphuric  acid  (oil  of  vitriol)     -     8  ounces. 
Water  4  " 

Should  any  pieces  of  zinc  be  left  after  twenty-four 
hours'  standing,  more  acid  should  be  added  until  they 
entirely  disappear.  Then  dilute  the  now  black  mass 
with  water,  slightly  acidulated  with  sulphuric  acid, 
and,  after  agitating  the  mixture  for  a  short  time,  let 
the  solution  remain  at  rest  until  the  whole  of  the 
black  powder  has  settled  to  the  bottom.  Now  decant 
the  water,  throw  the  black  muddy  mass  upon  a  filter 
and  wash  copiously  with  hot  water.  Finally,  dry  the 
contents  of  the  filter  and  ihe  result  is  pure  metallic 
silver  in  a  state  of  minute  division.  It  should  be  care- 
fully x^reserved  in  well  stoppered  glass  bottles  from 
dust  and  other  foreign  substances.  When  this  pro- 
cess is  conducted  properly  the  result  is  chemically 
pure.  Great  care  is  however  necessary  to  continue 
the  washing  long  enough,  as  otherwise  the  metallic 
silver  obtained  is  contaminated  with  zinc,  and  is  en- 
tirely unfit  for  photographic  purposes. 

2.  Into  some  freshly  precipitated  chloride  of  silver, 
hang  strips  of  copper  or  throw  some  copper  coin,  and 
acidulate  the  mixture  with  a  few  drops  of  oil  of  vitriol. 
After  twenty-four  hours'  standing  the  copper  will  be 
incrusted  with  metallic  silver;  but  the  copper  should 

4* 


94 


THE  KEDUCEr's  MANUAL. 


remain  in  tlie  mass  until  all  of  the  cliloride  is  trans- 
muted to  the  metallic  state,  which  can  be  readily  as- 
certained. Then  like  the  former  the  mass  should  be 
diluted  with  plenty  of  water,  the  gray  metalHc  powder 
allowed  to  settle  to  the  bottom,  and  the  incrustation 
removed  from  the  copper  strips,  the  whole  mass 
thrown  upon  a  filter,  washed  with  the  acidulated 
water,  and  finally  with  pure  hot  water  and  dried. 
The  result  is,  as  in  the  former  case,  pure  metallic 
silver. 

In  both  the  foregoing  processes  the  chloride  should 
be  mixed  to  about  the  consistency  of  cream  with  water. 

3.  Instead  of  using  strips  or  small  pieces  of  zinc, 
substitute  fragments  of  iron.  Proceed  precisely  as  in 
formula  first,  and  the  metallic  silver  obtained  will  be 
very  pure. 

4.  Place  the  chloride  of  silver  to  be  reduced  in  a 
convenient  vessel,  and  throw  in  it  a  strip  of  copper 
connected  with  the  zinc  end  of  a  battery.  In  a  day  or 
so  the  whole  of  the  chloride  of  silver  is  reduced  to  the 
metallic  state,  in  the  form  of  a  beautiful  incrustation 
on  the  copper. 

5.  The  chloride  of  silver  may  easily  be  reduced  to 
pure  silver  without  the  aid  of  fire.  Keep  the  salt 
under  water  in  the  dark-room  until  you  have  enough 
to  operate  upon,  and  time  to  devote  to  the  operation. 
The  following  is  the  mode  of  reduction: 

Take  a  bar  of  clean  zinc  as  heavy  as  the  quantity  of 
chloride  to  be  reduced,  and  solder  to  one  end  of  it  a 
silver  wire;  then  cover  the  zinc  completely  with  fine 
gauze  or  muslin  and  dip  it  in  clean  water.  Now  im- 
merse the  zinc,  so  covered,  in  the  moist  cliloride  of 


THE  EEDUCEr's  MANUAL. 


95 


silver,  and  bend  over  the  otlier  end  of  the  silver  wire, 
so  as  to  come  in  contact  with  the  chloride  of  silver  at 
a  short  distance  from  the  remote  end  of  the  zinc.  The 
operation  is  best  conducted  in  the  dark-room.  The 
moment  the  connection  is  made  with  the  silver  wire 
and  the  chloride,  an  electric  current  sets  in  and  de- 
composes the  chloride  of  silver  into  pure  silver,  which 
manifests  itself  first  at  the  loose  end  of  the  silver  wire. 
The  chlorine  which  is  set  free  hastens  through  the 
muslin  and  combines  with  the  zinc,  forming  chloride 
of  zinc,  a  very  soluble  salt  which  remains  in  solution. 
The  operation  may  continue  until  all  the  white  chlo- 
ride has  changed  color  and  become  silver  gray.  The 
bar  of  zinc  is  now  taken  out  and  washed  to  remove  any 
adhering  silver;  it  is  much  lighter  than  it  was  before 
the  operation.  Dilute  sulphuric  acid  is  added  to  the 
silver  powder  in  order  to  dissolve  any  particles  of  zinc; 
after  settling  a  number  of  hours  the  supernatant  liquid 
is  poured  away,  and  the  residue  is  well  washed  in  sev- 
eral changes  of  water.  The  residue  is  pure  silver  con- 
taining still,  probably,  some  undecomposed  chloride  of 
silver  which  is  no  injury  to  it. — Photographer's  Guide. 

This  is  a  rather  unnecessarily  compHcated  arrange- 
ment, and  the  results  are  not  as  good  or  certain  as 
with  anyone  of  the  foregoing  ones.  We  give  this  de- 
scription not  as  having  our  recommendation,  but,  on 
the  contrary,  we  do  so  only  to  have  the  chapter  as 
complete  as  possible. 

Sulphate  of  Silver. 

When  old  solutions,  etc.,  etc.,  have  been  precipitated 
in  the  form  of  a  sulphate,  the  still  wet  powder  may  be 


96 


THE  reducer's  MANUAL. 


readily  reduced  to  the  metallic  condition,  for  which 
proceed  as  follows: 

1.  Place  the  recently  precipitated  white  powder  in  a 
bowl  or  evaporating  dish,  and  upon  each  ounce  pour 
two  ounces  of  the  following  solution  : 

Sulphate  of  iron        -      -       -     4  ounces. 

Water  12  " 

Oil  of  vitroil      -       -       -       -     4  drops. 

After  thoroughly  mixing  the  mass  place  it  in  a  warm 
place  and  allow  it  to  remain  there  for  twenty-foui: 
hours.  Then  dilute  the  mass  copiously  with  warm 
water,  throw  the  result  on  a  filter,  and  wash  thor- 
oughly first  with  hot  water  acidulated  with  sulphuric 
acid,  and  then  with  hot  water  alone. 

The  result  is  pure  metallic  silver,  which  is  usually 
found  in  the  mass  in  the  form  of  little  thin  metallic 
tablets. 

2.  Connect  the  sulphate  with  the  zinc  end  of  the 
battery  by  means  of  a  strip  of  copper,  and  let  the 
action  proceed  until  the  whole  of  the  sulphuric  is 
changed  to  the  metal. 

Old  Nitrate  of -Silver  Baths,  Waste  Nitrate  Solutions,  etc. 

To  reduce  old  solutions,  etc.,  of  nitrate  of  silver  to 
the  metallic  state,  it  is  not  necessary  that  they  be  pre- 
viously precipitated,  but  they  may  be  treated  as  follows : 

1.  Hang  a  broad  and  long  strip  of  copper  in  the 
nitrate  solution,  and  allow  the  silver  to  deposit  on  it 
for  several  days.  Should  the  strip  of  sheet  copper  be 
consumed,  hang  in  another  one  and  allow  the  whole 
solution  to  remain  at  rest  as  long  as  any  deposition 


THE  KEDUCEr's  MANUAL. 


97 


takes  place.  Wlien  this  action  lias  ceased  remove  the 
remaining  copper  from  the  solution,  scrape  off  the  ad- 
hering silver  and  wash  the  resulting  powder  as  the 
last. 

2.  Eepeat  the  above  process  connecting  the  copper 
strip  with  the  zinc  end  of  the  battery,  and  the  process 
will  be  finished  almost  in  as  many  hours  as  it  takes 
days  in  the  former. 

3.  Kepeat  the  first  process,  substituting  zinc  for 
copper.    The  result  is  not  so  good. 

Neither  the  iodide,  the  bromide  or  the  sulphide  of 
silver  can  be  treated  by  the  galvanic  current. 

There  is  yet  another  way  in  which  chloride  of  silver 
may  be  very  economically  treated  in  the  wet  way,  and 
in  which  there  is  no  contamination  of  the  silver  by 
another  metal  to  be  feared,  it  is  as  follows: 

Place  in  a  bowl  or  flask  the  recently  precipitated 
chloride,  and  pour  upon  each  ounce  two  to  three  ounces 
of  the  following  solution: 

Caustic  potash  -      -      -      -     8  ounces. 
"Water      -      -      -      -      -    12  " 
Loaf  sugar       -      -      -      -     3  " 

Boil  the  chloride  in  this  liquid  for  about  half  an 
hour,  or  until  the  white  chloride  has  changed  to  a 
dark  brown  or  even  black  color;  then  dilute  copiously 
with  water,  throw  the  black  powder  upon  a  filter,  and 
wash  thoroughly  with  water.  Finally,  dry  and  pre- 
serve in  well  stoppered  bottles  for  future  use. 

The  potash  changes  the  chloride  into  the  oxide  of 
silver,  and  this,  in  time,  is  again  transmuted  by  the 
reducing  action  of  sugar  into  metallic  silvei'. 


98 


THE  BEDUCER's  MAKUAL. 


In  this  case  no  electricity  is  excited,  but  the  reduc- 
ing action  is,  nevertheless,  complete. 

The  Apparatus. 

The  apparatus  required  for  the  operations  mentioned 
in  the  preceding  pages  is  very  simple,  and  of  a  pre- 
cisely similar  character  as  that  used  for  treating  the 
liquid  residues  preparatory  to  smelting.  (See  page  56. ) 

"When  the  chloride  of  silver  is  to  be  reduced  by  the 
action  of  metallic  zinc,  a  beaker  or  precipitating  glass 
is  a  very  convenient  vessel.  The  zinc  should  be  in 
the  form  of  small  tablets  or  plates,  so  as  to  expose  a 
a  large  surface  to  the  action  of  the  acid. 

The  most  convenient  way  is  to  use  the  granulated 
metal.  For  this  purpose  the  zinc  is  placed  in  an  iron 
spoon  or  ladle,  and  brought  to  thorough  fusion,  then 
poured  into  a  pail  of  water  from  the  height  of  about 
four  feet.  When  copper  is  made  use  of  it  should  al- 
ways be  in  the  form  of  a  thin  strip  or  tablet.  The 
quickest  and  best  way  to  reduce  silver  is,  however,  as 
already  shown,  by  means  of  a  galvanic  battery,  which 

Fig.  10. 


for  this  purpose  may  be  of  very  simple  construction. 
The  one  best  adapted  for  reductions  is  that  known  as 


THE  BEDUCEk's  MANUAL. 


99' 


Smee's,  represented  by  Figure  10.  It  consists  of  two 
plates  of  zinc  clamped  to  a  piece  of  wood,  and  con- 
nected together  by  means  of  a  strip  of  brass  ending  in 
a  screw  cup  for  the  reception  of  tlie  conducting  wire. 

Between  tlie  zinc  plates  (which  should  be  about 
half  an  inch  apart)  is  suspended  a  thin  sheet  of  platin- 
ized silver,  which  is  also  connected  with  a  screw  cup, 
and  forms  the  second  pole  of  the  battery. 

This  combination  is  hung  in  a  proper  glass  vessel, 
which,  when  the  battery  is  to  be  set  in  action,  is  nearly 
filled  with  the  following  mixture: 

Sulphuric  acid  -      -      -       -     2  ounces. 
Water       -      -      -      -      -    16  " 

The  chloride  of  silver  of  about  the  consistency  of 
cream  is  poured  into  a  convenient  vessel,  and  in  it  is 
suspended  two  strips  of  copper,  but  not  touching  each 
other. 

The  chloride  will  now  be  seen  to  change  rapidly  in 
color,  and  a  deposit  of  pure  silver  to  collect  on  the 
copper  attached  to  the  zinc  end  of  the  battery,  while 
the  other  strip  is  dissolved  correspondingly  fast. 

This  form  of  battery  is  the  quickest,  but  one  quite 
sufficient,  for  moderate  quantities  of  wastes  may  be 
put  together  as  follows:  . 

Provide  two  pieces  of  zinc  and  two  pieces  of  copper 
about  4x6  inches  in  size.  Have  one  piece  of  copper 
connected  with  one  piece  of  zinc  by  means  of  a  thin 
strip  or  wire  of  copper  soldered  to  each,  and  the  other 
two  pieces  may  have  two  separate  wires  about  two  feet 
in  length  attached  to  them.  When  this  arrangement 
is  complete,  place  the  two  pair  of  metal  combinations 


100 


THE  BEDUCEB's  MANUAL. 


in  two  separate  glass  or  porcelain  vessels,  as  repre- 
sented by  rigure  11.    To  set  this  little  battery  in  op- 
Fig.  11. 


eration  the  cups  are  filled  with  strong  salt  \vater  or 
dilute  vinegar  as  follows: 

Strong  vinegar  -      -      -      -     4  ounces. 
Water  4  " 

Connect  the  wires  to  two  pieces  of  copper,  as  in  the 
last,  and  let  them  remain  in  the  chloride  for  about 
twenty-four  hours,  changing  the  salt  water  once  during 
this  time.  A  complete  reduction  is  effected  in  from 
one  to  two  days,  w^hile  with  a  Smee's  battery  it  is  ac- 
complished in  a  tenth  of  this  time. 

Great  care  must  always  be  taken  to  wash  the  re- 
duced mass  with  water,  acidulated  with  sulphuric  acid. 

Stronger  acid  may  be  used,  if  a  plug  of  asbestos  is 
placed  into  the  neck  of  the  funnel  as  a  filter. 


CHAPTEE  VII. 


QUANTITATIVE   ESTIMATION  OF   THE  PBECIOUS  METALS  CON- 
TAINED IN  WASTES  AND  ASHES. 

The  large  extent  to  whicli  fraud  is  committed  in  the 
reduction  of  gold  and  silver  residues — aided  and  ren- 
dered easy  by  the  photographer's  lack  of  knowledge  of 
the  first  principles  of  chemistry — has  made  It  absolutely 
necessary  that  some  mode  of  estimating  the  amount 
of  the  precious  metal  contained  in  his  residue  be  made 
known  to  him.  Though  it  is  an  easy  thing  for  a 
chemist  in  his  laboratory  to  test  in  a  few  moments,  at 
least  approximately  correct,  the  amount  of  precious 
metal  in  a  certain  substance,  still  for  an  unexperienced 
person  it  is  anything  but  an  easy  operation.  When  a 
simple  substance,  like  the  chloride,  iodide,  bromide, 
sulphide,  or  nitrate  of  silver  is  under  consideration, 
the  amount  of  metallic  silver  to  be  derived  from  any- 
one of  these  substances  is  readily  determined,  and  is 
but  a  simple  arithmetical  problem.  The  chloride  of 
silver  has  the  formula  of  AgCl,  and  consists  of  an  atom 
of  silver  combined  with  one  of  the  gas  chlorine ;  the 
bromide  AgBr,  one  atom  of  silver  and  one  of  bromine; 
the  iodide  Agl,  one  of  silver  and  one  of  iodine  ;  the 
sulphide  AgSg,  one  of  silver  and  two  of  sulphur;  and 
finally,  the  nitrate  AgNO^,  one  atom  of  silver  combined 
with  one  of  nitric  acid  (NO5),  or  otherwise,  one  atom 


102 


THE  reducer's  MANUAL. 


of  silver  combined  witli  one  of  nitrogen  and  five  of 
oxygen. 

To  estimate  tlien,  for  instance,  the  amount  of  metal" 
lie  silver  contained  in  a  given  quantity  of  the  chloride, 
we  proceed  as  follows: 

The  atomic  weight^  of  metallic  silver  is  108  and  that 
of  chlorine  35,  then  by  adding  108  and  35  together, 
we  obtain  143  as  the  atomic  weight  of  chloride  of 
silver.  Finally,  if  we  divide  108,  the  atomic  weight  of 
metallic  silver,  by  143,  the  atomic  weight  of  the  chlo- 
ride, we  have  remaining  in  the  quotient  the  decimal 
•75524,  which  equals  (allowing  for  loss  in  reduction) 
y^^j^  or  |.  Every  sixteen  ounces  of  chloride  of  silver 
are  consequently  equivalent  to  twelve  ounces  of  metal- 
lic silver,  or  seventy-five  per  cent,  of  the  chloride  con- 
sists of  metallic  silver.  Where,  as  in  the  sulphide  of 
silver,  there  are  two  equivalents  of  the  .  non-metallic 
body,  the  arithmetical  process  is  the  same,  but  the 
atomic  weight  of  the  non-metallic  body  must  be  doub- 
led, as  it  has  two  equivalents.  (AgSg.)  "Where,  as  in 
nitrate  of  silver,  there  are  two  haloids,  or  non-metallic 
substances  (AgNOg),  their  atomic  weights  are  added 
together,  while  the  atomic  weight  of  the  last  one,  oxy- 
gen, is  multiplied  by  five. 

With  the  knowledge  of  the  atomic  weight  of  the 
component  parts  of  a  body,  it  is  easy  for  us  to  calcu- 
late the  amount  of  metal  which  they  contain,  and  en- 
ables us  to  make  the  following  table : 

*  If  in  a  compound  of  one  grain  of  hydrogen  with  eight  of  oxygen  there 
be  an  equal  number  of  atoms  of  each,  an  atom  of  the  latter  will  be  eight 
times  as  heavy  as  an  atom  of  the  former.  In  this  way  we  know  the  rela- 
tive weights  of  the  atoms  of  all  substances,  whose  equivalents  are  known. 


THE  reducer's  MANUAL. 


103 


o  <J3  O  rrl 


a 


c3 

5^ 


CD 


S  c3 


c3 
O 


ID 


03 


Ah 


03 


> 


03 


^  C3 


S3 


o 

CI 


o 
Eh 


lO 

•77142 

ip 

lO 

•93102 

•79411 

•63529 

o 

o 

o 

GO 

CO 

TH 

CO 

tH 

rH 

tH 

AgCl 

□Q 
<1 

AgBr 

t— ( 

to 

<1 

o 

<1 

o 
o 

o 

Iver... . 

Lve 

ve 

ver. 

m 

*^ 

r-H 

o 

O 

O 

*5q 

03 

03 

03 

o 

Ihlori 

o 

xlide 

1— 1 

C3 

O 


o 


c3 

o 


104 


THE  reducer's  MANUAL. 


This  table,  as  v/ill  be  immediately  seen,  applies 
merely  to  tlie  pure  and  simple  compounds  of  silver, 
and  such  residues  as  paper  ashes,  collodion  films,  de- 
veloper washings,  etc.,  etc.,  cannot  be  estimated  in 
this  manner,  as  they  consist  of  several  diverse  sub- 
stances. To  find  correctly  the  amount  of  metallic 
silver  contained  in  ashes  or  other  wastes  not  comprised 
in  the  above  table,  it  is  necessary  to  analyze  a  small 
portion  and  thus  to  test  the  precise  amount  by  actual 
experiment.  This  may  be  done  in  several  different 
ways,  but  the  simplest  is  to  mix  a  drachm  or  so  of  the 
powder  under  consideration  with  a  little  borax,  say 
weight  for  weight,  and  to  expose  the  mixture  in  a  very 
little  crucible  (quarter  ounce)  to  a  brisk  heat  in  an 
ordinary  kitchen  fire.  The  little  pot  should  be  well 
embedded  in  the  glowing  coals,  and  the  reduction  will 
be  complete  in  from  fifteen  to  thirty  minutes.  The 
little  crucible  should,  when  the  desired  result  is  at- 
tained, be  removed  from  the  fire,  allowed  to  cool,  and 
finally  broken  open  with  a  hammer,  when  the  metaUic 
silver  will  be  found  at  the  bottom  in  the  form  of  a 
little  button  or  lump,  which  varies  in  size  from  the 
bead  of  a  pin  to  a  small  pea.  On  accurately  weighing 
the  little  button  it  is  easy  to  calculate  the  amount  of 
metallic  silver  to  be  derived  from  the  amount  of  ashes 
the  operator  may  have  in  his  possession.  Supposing 
the  yield  from  one  drachm  is  85  grains,  by  multiplying 
by  8  we  obtain  280  grains  as  the  yield  from  one  ounce 
of  ashes,  and  by  again  multiplying  by  16  we  obtain 
4,480  grains,  and  by  dividing  this  sum  by  360  (the 
amount  of  grains  in  one  ounce)  we  obtain  12  ounces 
and  108  grains  as  the  yield  from  one  pound  of  ashes. 


THE  reducer's  MANUAL. 


105 


By  these  means  the  operator  may  readily  ascertain,  in 
a  few  moments,  the  precise  amount  of  the  precious 
metal  contained  in  any  one  of  his  residues,  and  he  may 
consequently  readily  defend  himself  against  fraud  or 
imposition  on  the  part  of  the  refiner. 

But  the  process  just  given  is  open  to  several  objec- 
tions. In  some  galleries,  for  instance,  there  is  no  stove 
at  hand;  again,  the  manipulations  are  the  same  as  in 
reducing  large  quantities,  and  there  is  almost  as  much 
trouble  incurred  in  thus  testing  a  drachm  of  the  resi- 
due as  in  reducing  a  whole  pound  of  it.  These  objec- 
tions are,  however,  readily  overcome  by  the  use  of  a 
blowpipe. 

"  The  blowpipe  is  a  small  and  convenient  instru- 
ment by  which  a  blast  of  air  may  be  forced  through  a 
lamp,  gas-flame,  or  even  a  candle-flame,  so  as  to  inten- 
sify the  heat  of  the  latter  to  such  an  extent  as  to 
render  it  a  substitute  for  the  furnace  in  very  minute 
and  delicate  operations. 

"  A  simple  form  of  the  blowpij)e,  and  that  originally 
adopted  for  soldering,  etc.,  by  metal  workers,  is  repre- 
sented by  Figure  12.  It  consists  of  a  tapering  tube 
of  brass,  curved  nearly  at  a  right  angle  a  short  dis- 
tance from  the  smaller  end.    The  hole  terminates  in  a 


Fig.  la 


■  1 

fine  perforation.  A  steady  stream  of  air  is  forced  through 
the  pipe  by  the  action  of  the  muscles  of  the  cheeks,  and 
directed  against  the  flame  of  a  candle  or  lamp." 


106 


THE  BEDUCEr's  MANUAL. 


There  is  considerable  practice  necessary  to  use 
the  blowpipe  successfully;  but,  when  once  learned,  it 
is  a  pleasant  and  useful  acquirement.  To  make  the 
manner  of  using  the  mouth  blowpipe,  and  acquiring 
the  knack  of  breathing  and  blowing  at  the  same  time  plain 
to  the  reader,  we  make  an  extract  upon  this  subject 
from  "  Bowman's  Practical  Chemistry:" 

Before  proceeding  to  any  blowpipe  experiments,  it 
is  necessary  to  acquire  the  knack  of  keeping  up  a  con- 
stant and  unremitting  blast  of  air  from  the  mouth,  as 
without  this  it  is  impossible  to  raise  the  heat  to  a  suf- 
ficient degree  of  intensity.  The  habit  is  readily  ac- 
quired, and  when  once  attained,  the  mouth  and  lungs 
will  be  found  to  do  their  work  almost  mechanically, 
without  any  sustained  effort  on  the  part  of  the  op- 
erator. 

"  The  learner  may  first  observe  that  on  closing  the 
lips  he  can  still  without  difficulty  breathe  through  the 
nostrils  :  let  him  now  distend  the  cheeks  with  air 
from  the  lungs,  and  he  will  find  that  on  closing  the 
communication  between  the  mouth  and  throat  he  can 
breathe  through  the  nostrils  for  a  length  of  time,  still 
keeping  the  cheeks  distended.  He  may  next  introduce 
the  mouth-piece  of  the  blowpipe  between  his  lips,  and 
having  puffed  out  his  cheeks  with  air  from  the  lungs, 
and  again  closed  the  communication  between  the 
mouth  and  throat,  let  him  breathe  freely  through  the 
nostrils,  at  the  same  time  allowing  the  distended 
cheeks  to  force  a  current  of  air  through  the  blowpipe. 
"When  the  stock  of  air  in  the  mouth  is  nearly  ex- 
hausted, a  fresh  supply  is  sent  up  from  the  lungs, 
when  the  cheeks,  again  distended,  nvill  by  their  elas- 


THE  EEDUCEr's  MANUAL. 


107 


ticity  keep  up  a  current  of  air  through  the  blowpipe, 
while  the  operator  breathes  through  the  nostrils  as 
before. 

"  The  cheeks  thus  play  the  part  of  an  elastic  bag, 
with  a  valve  opening  inward,  which,  if  connected  with 
the  blowx3ipe,  and  distended  with  air,  would  force  air 
through  it  as  long  as  the  tension  of  its  stretched  sides 
exerted  sufficient  pressure." 

Having  now,  we  will  suppose,  acquired  the  knack 
of  using  the  blowpipe,  it  is  an  easy  matter  to  estimate 
quantitatively  every  existing  gold  or  silver  residue. 
Weigh  out  very  accurately  about  fifteen  grains  of  the 
residue,  and  add  to  it  fifteen  grains  of  a  mixture  of 
equal  parts  of  carbonate  of  soda  and  cyanide  of  pot- 
ash. Then  obtain  a  piece  of  pine  or  willow  charcoal 
and  scoop  a  cavity  in  it,  just  large  enough  to  contain 
the  above  mixture;  then  support  the  blowpipe  on  the 
edge  of  the  flame  of  a  lamp  or  candle,  and  blow  a 
steady  fine  flame  upon  the  mixture.   (Figure  13.)  The 

Fig.  13. 


residue  soon  begins  to  glov/,  to  melt,  and  bubble,  and 
finally  the  globule  of  silver  will  be  seen  dancing  about 


108 


THE  KEDUCER's  MANUAL. 


in  the  glowing  cavity.  Wlien  the  reduction  has. been 
completed,  allow  the  charcoal -and  contents  to  cool, 
remove  the  globule  of  silver  by  means  of  a  little  pair 
of  nippers,  and  wash  thoroughly  from  any  adhering 
flux.  By  weighing  the  result  on  a  delicate  balance, 
the  precise  amount  of  metallic  silver,  contained  in  the 
residue  on  hand,  may  be  estimated.  No  matter  what 
the  residue  may  consist  of  the  flux  in  this  operation 
should  be  always  the  same — equal  parts  of  carbonate 
of  soda  and  cyanide  of  potash.  If  the  flame  be  skill- 
fully managed  the  residue  should  be  complete  in  about 
five  minutes. 

The  great  beauty  and  simplicity  of  the  blowpipe 
process  must  be  apparent  to  every  reader.  The  trouble 
incurred  is  so  small  and  the  result  is  so  accurate,  that 
this  mode  of  estimation  should  be  made  use  of  in  every 
case  where  the  residues  are  sent  to  smelters  or  refiners 
for  reduction.  By  this  process  the  photographer  and 
silver  worker  may  accurately  estimate  the  value  of 
waste  sent  to  the  refiner. 

In  estimating  the  residues,  care  should,  of  course,  be 
taken  to  obtain  a  fair  average  of  the  sample  under  con- 
sideration. For  this  purpose  the  ashes  or  other  wastes 
should  be  carefully  sifted  through  a  fine  flour  sieve, 
and  all  glass  and  other  foreign  matter  removed,  while 
any  lumps  of  chloride  of  silver  contained  therein,  are 
ground  to  powder  and  mixed  evenly  throughout  the 
sifted  mass. 

There  is  no  way  of  estimating,  at  least  very  accu- 
rately, by  the  v/et  way  the  amount  of  metallic  silver 
contained  in  a  residue. 

When  arithmetically  calculating  the  amount  of  silver 


THE  reducer's  MANUAL.  109 

contained  in  one  of  its  compounds,  we  must,  however, 
bear  in  mind  that  the  actual  yield  is  never  so  large  as 
the  calculated  one,  for,  as  a  general  rule,  the  residues 
are  not  pure,  but,  on  the  contrary,  more  or  less  con- 
taminated with  foreign  impurities.  Thus,  for  instance, 
the  precipitate  of  the  print  washings,  generally  called 
chloride  of  silver,  and  which  would  consequently  be 
calculated  to  contain  or  |  its  weight  of  metallic 
silver,  generally  yields  actually  only  fifty  to  sixty-five 
per  cent,  (according  to  the  way  it  has  been  saved),  on 
account  of  the  large  amount  of  albumen  it  contains. 

Then  again,  when  estimating  about  fifteen  grains,  as 
above  directed,  the  reduction  is  necessarily  much  more 
complete  than  when  pounds  of  the  residue  are  reduced 
at  once,  and  a  small  percentage  should  be  allowed  for 
loss  in  this  way.  In  all  cases  where  any  doubt  exists 
as  to  the  purity  of  a  compound  (for  only  such  can  be 
arithmetically  estimated),  a  small  portion  of  the  sub- 
stance under  consideration  should  be  reduced  with  the 
blowpipe,  as  before  directed,  as  then  only  a  certain 
and  correct  estimation  can  be  made.  The  impure 
chloride  of  silver  obtained  from  print  washings,  can  be 
very  correctly  determined  without  heat  as  follows: 

Place  one  drachm  (thirty  grains)  of  the  well  dried 
print  washing's  precipitate  in  a  small  evaporating  dish 
or  other  convenient  vessel,  and  pour  upon  it  one  ounce 
of  a  supersaturated  solution  of  caustic  potash,  and  let 
it  heat  for  a  few  minutes  on  a  stove.  When  the  chlo- 
ride has  changed  to  a  dark  brown  or  black,  dilute  the 
mass  with  eight  ounces  of  water  and  let  the  precipitate 
settle ;  wash  a  few  times  in  this  manner,  then  throw 
upon  a  filter  (better  a  tuft  of  cotton  in  the  neck  of  a 
5 


110 


THE  EEDUCER's  MANUAL. 


funnel),  and  let  the  liquid  run  through.  Collect  the 
brown  powder  carefully,  dry  it  thoroughly,  and  if 
much  remains  upon  the  cotton  tuft,  burn  this  and  add 
the  ashes  to  the  rest  of  the  powder.  When  it  is  com- 
pletely dry  throw  the  powder  on  a  delicate  balance, 
and  referring  to  our  table  for  "  Oxide  of  Silver  "  the 
amount  of  metallic  silver  can  be  readily  determined. 
By  the  above  process  all  of  the  albumen  is  removed  by 
means  of  the  potash,  and  the  estimation  is  as  correct 
as  by  fusion  with  the  blowpipe. 

To  estimate  the  amount  of  silver  contained  in  ashes 
the  mode  of  procedure  is  as  follows:  Place  half  an 
ounce  of  the  ashes  (which  for  this  purpose  should  be 
thoroughly  burnt)  in  a  small  evaporating  dish  or  a 
beaker  glass,  and  pour  upon  these  about  two  ounces 
of  strong  nitric  acid  and  one  ounce  of  water.  Set  the 
mixture  upon  the  stove  and  let  it  boil  rapidly  nearly  to 
dryness;  then  dilute  the  mass  with  four  or  five  ounces 
of  water,  and  filter  through  a  plug  of  cotton  placed  in 
the  neck  of  a  funnel.  The  clear  filtrate  is  placed  in  a 
clean  evaporating  dish  and  boiled  rapidly  to  dryness. 

The  crystalline  mass  of  nitrate  of  silver  should  be 
carefully  dried  and  estimated  according  to  Nitrate 
of  Silver"  on  our  table;  or  it  may  be  reduced  very 
easily  on  charcoal,  by  a  few  puffs  from  the  blowpipe, 
and  the  resulting  metal  carefully  weighed;  one  can 
estimate  approximately  correct  the  amount  of  silver 
the  ashes  will  yield.  It  will  be  seen  by  the  foregoing 
processes  that  the  estimation  of  residues  by  the  wet 
way  is  nothing  more  than  the  reduction  of  a  small 
portion  of  the  same,  and  the  blowpipe  is  merely  a 
miniature  furnace,  in  which  all  the  operations  of  re- 


THE  KEDUCEb's  MANUAL. 


Ill 


dticing  are  performed  on  a  small  scale.  Many  other 
ways  of  estimating  residues  by  the  wet  way  will  be  sug- 
gested to  the  reader  by  the  perusal  of  Chapter  VI., 
as,  for  instance,  the  estimation  of  developer  residues. 

PRACTICAL  SUGGESTIONS. 

The  main  thing  necessary  to  obtain  a  correct  esti- 
mate of  the  amount  of  silver  contained  in  a  substance 
is  a  delicate  balance  or  scale,  which  should  turn  at 
least  the  one-twenty-fifth  of  a  grain.  A  balance  very 
suitable  for  weighing  small  quantities  of  silver,  or  the 
iodides  and  bromides  in  the  preparation  of  collodion 
for  photographic  purposes,  may  be  readily  constructed 
with  a  little  care  and  ingenuity  as  follows : 

Have  two  little  scale  pans^  two  inches  in  diameter, 
punched  out  for  you  by  the  tinsmith,  and  put  three 
holes  in  each  of  equal  distances  apart.  A  silk  thread 
is  tied  into  each  one  of  these  holes,  and  they  are  then 
knotted  together,  and  a  silken  thread,  three  inches  or 
so  in  length,  connected  to  these.  A  thin  straight  piece 
of  wire  should  now  be  provided,  and  one  of  the  pans 
connected  to  each  end  of  this  wire.  In  precisely  the 
middle  of  the  wire  should  be  secured  a  strip  of  wood, 
about  the  length  and  size  of  a  match,  and  to  this  two 
pieces  of  silk  thread,  about  three  inches  in  length, 
which  for  convenience'  sake  may  end  in  a  brass  ring. 
To  illustrate  this  more  clearly  we  will  describe  the 
annexed  woodcut. 

A  A  are  the  scale  pans  connected  with  the  three 
silk  strings  B,  which  are  connected  to  a  hook  on  the 
wire  C,  which  {precisely)  in  the  middle  is  fastened  the 
strip  of  wood  D,  from  each  end  of  which  passes  a  silk 


112  THE  reducer's  MANUAL. 

thread  E,  -wliicli,  in  turn,  connects  with  the  single 
thread  F.    "When  the  middle  of  the  beam  is  correctly 

Fig.  14. 


balanced,  and  the  "whole  thing  properly  put  together, 
this  balance  is  of  wonderful  delicacy,  and  the  pans 
will  turn  readily  with  the  one-fiftieth  part  of  a  grain; 
and  we  once  even  constructed  one  on  the  same  prin 
ciple  that  turned  with  less  than  the  one  hundretb 
part  of  a  grain.  A  balance  of  like  delicacy  could  not 
be  purchased  for  less  than  $50. 

The  balance  should  be  so  suspended  that  the  pans 
are  within  a  quarter  of  an  inch  from  the  table  or  stand. 
A  convenient  way  to  suspend  the  balance  is  to  make 
a  little  stand  from  a  pine  board,  and  driving  a  wire 
with  a  hook  at  its  end  into  it,  as  represented  by  the 
accompanying  woodcut. 

When  not  in  use  the  balance  should  be  covered  from 
dust  or  dirt  by  a  glass  globe,  or  by  a  box  of  glass  made 
by  uniting  panes  of  glass  of  the  proper  size  by  means 
of  paper  or  cloth. 


THE  reducer's  MANUAL.  113 

Fig.  15. 


A  very  good  blowpipe  may  be  made  in  emergencies 
by  accurately  fitting  the  bowl  of  an  ordinary  tobacco 
pipe  with  a  tight  cork,  and  fitting  into  this  a  glass  jet 
or  an  inch  of  the  stem  of  a  pipe  having  a  very  minute 
lore. 


Fig.  16. 

m 

-  ,  .'J 

A  glass  jet  is  formed  by  drawing  out  a  glass  tube  to 
a  very  fine  point,  and  holding  it  into  the  flame  until  it 
thickens  at  the  end.  Finally,  file  a  small  hole  into  the 
top  with  an  ordinary  file.  When  residues  are  esti- 
mated a  test-tube  (a  thin  glass  tube  closed  at  one  end) 
may  be  used  instead  of  the  more  cumbersome  evapor- 
ating dish. 


CHAPTEE  VIII. 


USEFUL  HESTTS  AND  FORMULAS. 

We  would  in  every  case  advise  the  practical  photo- 
graphic operator  to  manufacture  nitrate  of  silver  from 
the  result  of  his  reductions,  in  preference  to  selling  it 
in  the  metallic  form  to  a  refiner,  as  the  loss  in  this 
case  is  at  least  fifteen  per  cent.,  and  often  much  more. 
It  is  a  general  impression  among  photographers,  that 
the  manufacture  of  a  pure  article  of  the  nitrate  is  at- 
tended with  much  difficulty;  this  is,  however,  not  the 
case,  unless  the  result  is  to  be  in  large  crystals,  when 
many  precautions  are  necessary.  If,  however,  the 
photographer  makes  the  nitrate  only  for  his  own  con- 
sumption, the  fine  snoio  crystals  obtained  by  rapidly 
evaporating  a  solution  of  the  nitrate  are  even  prefer- 
able, in  many  respects,  to  the  well  crystalized  salt. 
The  chief  point  to  be  observed  is  to  obtain  a  pure  and 
neutral  salt,  for  which  the  following  formula  answers 
admirably.  Only  the  purest  metallic  silver,  as  that 
obtained  from  the  chloride  or  well  refined,  should  be 
used  for  the  manufacture  of  the  nitrate.  Place  the 
well  granulated  metal  in  a  large  evaporating  dish,  and 
upon  each  ounce  pour  four  ounces  of  the  following 
mixture : 

Pure  nitric  acid  -      -      -      -     4  ounces. 
Water  5  " 


THE  reducer's  MANUAL. 


115 


Place  the  dish  upon  a  moderately  hot  stove,  and 
raise  the  mixture  gradually  to  the  boiling  point,  and 
let  it  simmer  for  about  thirty  minutes,  or  until  the 
generation  of  red  vapors  and  all  violent  chemical  ac- 
tion has  ceased;  then  remove  it  from  the  fire,  dilute  it 
with  an  equal  amount  of  water,  and  filter  the  liquid 
through  a  wad  of  cotton  placed  in  the  neck  of  a  fun- 
nel. If  it  should  not  be  clear  at  first,  it  must  be  fil- 
tered again,  then  poured  off  in  an  evaporating  dish, 
placed  upon  a  stove  and  evaporated  to  dryness.  "When 
the  liquid  has  all  evaporated,  the  rei^iaining  mass  of 
white  crystals  should  be  exposed  to  heat  imtil  they 
begin  to  assume  a  grayish  brown  color,  caused  by  the 
liberation  of  oxide  of  silver,  the  dish  must  then  be 
quickly  removed  from  the  fire,  allov/ed  to  cool,  and 
the  gray  mass  then  dissolved  perfectly  in  distilled 
water.  Finally,  filter  the  murky  liquid  and  dilute  it 
to  the  proper  strength  for  the  sensitizing  bath,  or 
evaporate  the  solution  to  dryness  and  preserve  the 
white  crystals  in  a  well  stoppered  glass  bottle. 

To  Make  Pure  Chloride  of  Gold. 

Place  the  metallic  gold  in  a  small  evaporating  dish 
or  beaker  glass,  and  upon  each  pennyweight  pour  two 
to  three  drachms  of  a  mixture  of  the  following  acids: 

Nitric  acid        -       -       -       -     3  ounces. 
Hydrochloric  acid     -       -       -  2 

Place  the  mixture  upon  the  stove  until  complete  so- 
lution takes  place  ;  then  dilute  with  some  distilled 
water  and  filter  the  yellow  liquid  until  perfectly  clear; 
then  place  it  in  a  small  evaporating  dish  and  expose  it 


116 


THE  EEDUCERS  MANUAL. 


to  a  gentle  heat  until  it  lias  boiled  off  to  thorougli  dry- 
ness. To  obtain  the  salt  of  great  purity,  it  may  be 
once  more  dissolved  in  a  little  distilled  water  and 
again  crystalized;  but  this  second  crystalization  is 
hardly  necessary.  The  -well  dried  mass  of  yellow 
crystals  should  be  rapidly  removed  from  the  dish  and 
placed  in  perfectly  dry  and  warmed  bottles. 

To  Make  Auro-Chloride  of  Sodium, 

Place  the  gold  in  the  form  of  powder  or  otherwise 
in  a  small  porcelain  dish  as  before,  and  pour  upon  it 
the  same  amount  of  acid  as  in  the  last. 

When  the  liquid  has  nearly  evaporated  to  dryness 
(the  second  time),  rapidly  and  thoroughly  stir  it  in  a 
quantity  of  clean  common  salt  to  equal  the  weight  of 
the  metallic  gold  used,  and  let  the  mass  then  crystal- 
ize  by  evaporating  the  liquid  to  dryness.  Preserve 
the  salt  in  well  stoppered  bottles  as  it  rapidly  absorbs 
moisture  from  the  air.  Or  the  solution  of  gold  may 
be  used  direct  without  evaporating;  but  the  solution 
should  have  been  already  once  boiled  down.  Both 
the  nitrate  of  silver  and  the  chloride  of  gold  prepared 
by  these  processes  are  of  great  purity.  The  nitrate 
of  silver  is  rendered  perfectly  neutral  by  exposing  the 
crystalized  mass  to  heat,  until  a  small  quantity  of  the 
oxide  of  silver  is  liberated,  and  the  chloride  of  gold 
by  double  crystalization. 

Another  Way  of  Making  Pure  Chloride  of  Gold. 

The  gold  should  be  placed  in  a  flask  or  glass  and 
covered  with  an  ounce  or  two  of  distilled  water. 
Then  chlorine  gas  is  led  into  the  water,  which,  soon 


THE  EEDUCEr's  MANUAL. 


117 


becoming  charged  with  it,  rapidly  attacks  and  dis- 
solves the  gold. 

The  yellow  solution  thus  resulting  must  be  evapor- 
ated to  perfect  dryness  in  a  suitable  vessel  and  treated 
precisely  like  the  last. 

To  generate  chlorine  a  small  glass  flask  should  be 
provided  with  a  tight  fitting  cork,  into  which  is  in- 
serted a  bent  glass  tube  or  India-rubber  gas  tube.  In- 
to this  flask  place  some  black  oxide  of  manganese,  and 
pour  upon  it  enough  muriatic  acid  to  make  it  of  the 
consistency  of  cream.  The  flask  is  then  placed  in 
boihng  water  or  heated  sand,  and  the  chlorine  rapidly 
generates  and  is  absorbed  by  the  water. 

To  Make  Pure  Nitrate  of  Silver  from  the  Oxide, 

The  simplest  process  for  the  manufacture  of  pure 
nitrate  of  silver,  and  that  involving  the  least  appar- 
atus and  time,  is  by  the  use  of  the  oxide  of  silver,  ob- 
tained either  by  the  precipitation  of  an  old  solution,  or 
by  the  action  of  caustic  potash  upon  the  chloride  of 
silver. 

Place  the  well  washed  and  stiU  wet  oxide  in  an 
evaporating  dish  of  proper  size,  and  add  slowly  the 
following  mixture  of  acids: 

Chemically  pure  nitric  acid       -     2  ounces. 
DistiUed  water  -      -      -      -     3  " 

As  soon  as  violent  chemical  action  takes  place,  the 
addition  of  acid  should  be  stopped,  the  dish  placed 
upon  a  sand  bath  and  brought  nearly  to  the  boiling 
point. 

If  any  black  powder  now  remains,  more  acid  should 
5* 


118 


THE  EEDUCER's  MANUAL. 


carefully  be  added,  drop  by  drop,  until  the  liquid 
becomes  perfectly  clear,  and  on  precipitation  remains 
in  the  solution. 

The  contents  of  the  dish  should  then,  if  necessary, 
be  thrown  upon  a  filter,  and  the  clear  filtrate  passing 
through  placed  in  a  porcelain  dish  and  rapidly  evap- 
orated to  dryness.  The  resulting  snowy  mass  consists 
of  pure  nitrate  of  silver,  and  should,  if  an  excess  of 
acid  has  been  added,  be  exposed  to  a  gentle  heat  until 
the  oxide  begins  to  form,  as  directed  above. 

Nitrate  from  the  Carbonate, 

When  the  silver  has  been  precipitated  in  the  form 
of  a  carbonate,  the  well  washed,  yellowish  brown  pow- 
der should  be  placed  into  an  evaporating  dish,  or 
beaker  glass,  and  treated  precisely  in  the  same  way  as 
the  former. 

The  results  of  both  of  these  processes  are  remark- 
ably pure,  provided  the  directions  above  given  are  ad- 
hered to. 

Testing  Nitrate  of  Silver  as  to  Purity. 

The  nitrate  of  silver  of  commerce,  and  that  sold  by 
most  stock  dealers  throughout  the  United  States,  is 
rarely,  if  ever,  perfectly  pure;  but,  on  the  contrary, 
often  contains  foreign  substances,  either  purposely 
mixed  with  it  as  an  adulteration  to  lesson  its  cost, 
or  allowed  to  enter  into  its  composition  by  careless- 
ness or  ignorance. 

Some  manufacturers,  for  instance,  add  nitrate  of 
potash  or  saltpeter  for  the  purpose,  they  say,  of  pro- 
ducing large  crystals ;  and  one  firm,  doing  a  very 


THE  KEDUCEr's  MANUAL. 


119 


heavy  business,  adds  as  mnch  as  half  an  ounce  to  every 
pound  of  nitrate.  "Whether  this  is  done  from  disinter- 
ested motives  or  not,  we  leave  the  photographer  to 
judge. 

The  operator  may  readily  test  the  purity  of  any  ni- 
trate of  silver  as  follows : 

Dissolve  five  grains  of  the  nitrate  in  a  drachm  of 
distilled  water,  and  when  complete  solution  has  taken 
place,  add  chemically  pure  hydrochloric  acid,  drop  by 
drop,  until  it  no  longer  gives  a  white  precipitate. 
Now  place  a  few  drops  of  the  clear  liquid  above  the 
sediment  on  a  thin  strip  of  platinum,  or  a  watch-glass, 
and  expose  it  to  a  gentle  heat.  If,  when  the  water 
has  boiled  off,  no  residue  is  left  on  the  surface,  the 
silver  is  pure;  if,  on  the  other  hand,  much  residue  is 
left,  it  is  impure  and  should  be  rejected.  Of  course 
the  acid  must  be  pure  and  the  water  distilled,  other- 
wise they  both  have  residues,  which  would  mislead 
the  examiner. 

One  valuable  hint  we  can  give,  that  is  never  bmj  cheap 
nitrate  of  silver,  as  it  is  invariably  impure,  the  profits 
on  a  pure  article  being  so  small,  that  only  the  largest 
houses  can  sell  it  with  a  profit.  No  workman  can  do 
good  work  without  proper  tools,  and  chemicals  maybe 
aptly  termed  the  tools  of  the  photographer.  This  is 
the  failing  of  many  of  our  operators.  They  work  with 
cheap  and  inferior  chemicals,  and  many  do  not  even 
know  their  composition,  to  say  nothing  of  their  reac- 
tion mutually  upon  each  other.  Without  a  thorough 
knowledge  of  photographic  chemistry,  the  operator 
cannot  possibly  arrive  at  that  standard  which  may  be 
truly  termed  Art  Photography. 


120 


THE  KEDUCEr's  MANUAL. 


WEIGHTS  AND  MEASURES. 


The  following  tables  of  the  corresponding  values  of 
French  and  English  weights  and  measures  will  be 
found  very  useful  for  reference,  as  the  decimal  system 
of  the  French,  owing  to  its  greater  convenience  for 
calculations,  is  extensively  adopted  in  chemical  works. 

The  unit  of  the  French  weight  is  the  gramme,  which 
is  the  weight  of  the  hundreth  part  of  a  cubic  metre  of 
distilled  water,  at  the  temperature  of  melting  ice.  Be- 
low are  some  comparative  tables,  which  will  serve  to 
give  every  explanation. 

Grammes.       Troy  Grains. 
Milligramme       =      -001      =  '01543 
Centigramme      =      '01        =  -15434 
Decigramme       =      -1         =  1*5434 

Troy  WeigJit, 
Troy  weights.  French  weights. 

1  grain  =  1-24  dwt.  =  0-06477  gramme. 

1  pennyweight   =  l-20th  of  an  ounce  =  1-55456  gramme. 
1  ounce  =  l-12th  of  a  lb.  Troy  —  31-09130  grammes. 

1  pound  imperial  =  0  3730956  kilogramme. 

Avoirdupois  Weight, 

English. 

1  drachm  =  1-1 6th  of  an  ounce  = 
1  ounce  =  l-16th  of  a  pound  = 
1  pound  or  1  pound  imperial  = 


1  cwt.  =  112  pounds 
1  ton         =  20  cwt. 


French. 
1-7712  gramme. 
28-3384  grammes. 
0  4534143  kilogramme. 
=     50-7824600  kilogrammes. 
=  1015-6490000  kilogrammes. 

Grammes.      Troy  Grains. 


Gramme  =  1 

Decigramme  =  10 

Hectogramme  =  100 

Kilogramme  =  1000 

Myriagramme  =  10000 


=  15-434 
=  154-34 

=z  ,  1543-4 
=  15434 

=  154340 


THE  REDUCEk's  MANUAL. 


121 


French.  English. 
1  gramme  =  15.438  grains  Troy  =  0-643  dwts.  =  0-03216  oz.  Troy. 
1  kilogramme  —  2-68027  lbs.  =  2  lbs.  8  oz.  3  dwts.  6  grs.  Troy  wt. 
1  kilogramme  =  2-20548  lbs.  =  2  lbs.  3  oz.  4  4-5  drs.  Avoirdupois. 
1  myriagramme  =  22*0485  lbs.  Avoirdupois. 
1  quintal  =  1  cwt.  3  qrs.  25  lbs. 

The  unit  of  superficial  measure  is  "  tlie  are,  a  surface 
of  ten  metres  each  way,  or  100  square  metres.  The 
unit  of  measures  of  capacity  is  the  litre,  a  vessel  con- 
taining the  cube  of  a  tenth  part  of  the  metre,  and 
equivalent  to  0*220097  parts  of  the  British  imperial 
gallon.    The  standard  temperature  is  32°  F.    AU  the 
divisions  and  multiples  of  the  units  are  decimal." 
Measures  of  Length. 
Myriametre       =       10,000  metres. 
Kilometre         =         1000  " 
Hectometre       =  100  " 

Metre  =  1  " 

Decimetre         =  0*1  " 

Centimetre        =  0*01  " 

Millimetre        =  O'OOl  " 

Measures  of  Surface, 
Hectare        =        1000  sq.  naetres. 
Are  =  100  " 

Centiare        =  1  " 


Measures  of  Capacity. 


Kilolitre 

1000 

litres. 

Hectolitre 

100 

(( 

Decalitre 

10 

(( 

Litre 

1 

litre. 

Decilitre 

01 

(( 

Centilitre 

0-01 

The  unit  of  the  solid  measure  is  the  stere,  or  cube 
of  the  metre,  equal  to  35*31658  English  cubic  feet. 


122 


THE  EEDUCER's  MANUAL. 


Measures  of  Length, 

English. 
1  inch  or  l-36th  of  a  yard  - 
1  foot  =  J-  of  a  yard  =  13  inches 
1  yard  =  3  feet  -      -      -  - 
1  fathom  =:  2  yards   -      -  - 
1  pole  or  perch  =  51  yards 
1  furlong  =  220  yards 
1  mile,  or  1760  yards  -      -  - 

French. 
1  millimetre 
1  centimetre 
1  decimetre 
1  metre 
1  decametre 
1  hectometre 
1  kilometre 
1  myriametre 


Long  Measure, 

French. 
=      2-539954  centimetres. 
=      3-0479449  decimetres. 
z=:      0-91438348  metre. 
=      1-82876696  " 
=      5-02911000  metres. 
=  201-16437000  ^* 
=  1609-31490000  " 

English. 


0039370 
0-393708 
3-937079 
39-37079  = 
393-7079  = 
3937-079 
39370-t9 
393707-9 


1-093633  yards. 
=  10-936630 
=  109-366300 

=  4  furlongs,  213-633  yards. 
=  6  miles,  1  furlong,  156*288  yards 

French.  English. 
1  toise  =  6-3945  feet  =  2*1315  yards  =  76-735  inches. 
1  aune  or  ell  —  3*893  feet  =  46*79  English  inches. 

Square  Measure, 
English.  French. 

1  sq.  yard  —  0*836097  metre  carre. 

1  rod  or  pole  =  30i  sq.  yards      -   =  25*291939  metres  carres. 

1  rood  ==  1210  sq.  yards       -      -   =  10*116775  ares. 

1  acre  =  4840  sq.  yards  =  40*4671  ares  =  0*404671  hectare. 

1  metre  carre  =:  1  centiare   -      -    =  1*196033  sq.  yard. 

1  are  =  3*95  English  poles    -      -   =  0*98845  rood. 

1  hectare  =  2  acres,  1  rood,  5  perches  =  2*473614  acres. 

Measures  for  Liquids, 

English.  French. 

1  pint  or  ith  of  a  gallon  =  0  567932  litre. 

1  quart  or  ith  of  a  gallon  =  1  135864  litres. 

1  imperial  gallon  =  4*5434579  " 


THE  EEDUCER's  MANUAL. 


123 


Dry  Measure. 
English.  French. 
1  peck         —   2  gallons  =   9-0869159  litres. 
1  bushel       =   8      "      =  36-347664  " 
1  sack  =   3  bushels  =    1-09043  hectolitre. 

1  quarter      =   8     "      =   2-907813  hectolitres. 
1  chaldron    =  12  sacks     =  13-08516  " 

French.  English. 
1  litre  =  1-760773  pints  =  -8803865  quarts  =    -2200966  gallons. 

1  decilitre  =  22009667 

1  hectolitre  =  22-0096670  " 

As  a  greater  convenience  for  common  purposes,  the 
French  denominations  were,  in  1812,  arranged  as 
follows: 

1  toise  or  6  feet  =  2  metres  =  6  5618334  English  feet. 
1  foot  or  12  inches  =  J-  metre  =  10936389  "  foot. 
1  inch  or  12  lines  -  -  =  1-0936389  inch. 
1  line        .      -      .      .    =  0-0911365      "  " 

1  aune  or  ell  =  1 1-5  metre  =  3  937  English  feet:— Or, 
1  aune    -      -      -      -   =  47*244      "  inches. 

1  bushel  =  i  hectolitre  =  762'85  cubic  inches. 

1  old  Paris  foot  =  1-066  English  foot. 
1  old  Paris  inch  =  1  066  "  inch. 
1  old  line         =  0-0888     "  " 

The  metre,  the  square  metre,  and  the  cubic  metre, 
are  the  radical  standards  of  the  three  measures;  for 
there  are  only  three,  as  solidity  and  capacity,  differ- 
ently named  and  used,  are  the  same  in  reality.  From 
these  radical  denominations,  namely,  the  metre  of  the 
lineal  measure,  the  are  of  the  superficial  measure,  the 
litre  of  measured  capacity,  and  the  stere  of  solid  or 
cubic  admeasurement,  the  larger  ones  are  procured  by 


124 


THE  reducer's  MANUAL. 


multiplying  by  ten,  and  the  lower  ones  by  dividing  by 
the  same.  Thus, 

Beca  prefixed,  means  10  times. 
Hecto,     "         "  100 
Kilo,       "         "  1000 
Myria,  '   "    10,000  " 

The  number  is  understood  to  multiply  the  surface 
of  the  solid  and  not  its  side.  Thus,  one  decare  is  ten 
ares,  not  a  square  of  ten  times  the  side  of  an  are,  and 
so  of  the  others. 

The  denominations  below  the  radical  ones  are  ex- 
pressed by  a  sort  of  Latin  prefix.  Thus, 

Deci  is  one-tenth. 
Centi  is  one-hundreth. 
Milli  is  one-thousandth, 

Morfit's  Chemical  Manipulations, 


PART  II. 


THE 

GOLD  WORKER'S  GUIDE: 

A  SHORT  AND  PBACTICAL  TREATISE  ON 

DISCOVERING,  ASSAYING,  ESTIMATING 

AND 

TESTING  ORES  AND  MINERALS 

CONTAINING 

GOLD  OR  SILVER. 


INTRODUCTION. 


Inexperienced  persons,  and  miners  not  having  tlie 
advantage  of  a  knowledge  of  chemistry,  have  often  felt 
that  imperative  want  of  a  simple,  short  and  practical 
treatise  on  gold  and  silver  ores,  the  way  of  discover- 
ing, testing  and  assaying  them.  There  is  not,  how- 
ever, Ave  believe,  a  single  popular  work  which  treats 
the  subject  in  a  practical  manner;  but,  on  the  con- 
trary, the  now-existing  works  are  replete  with  high- 
sounding  technical  expressions. 

Again,  what  great  dismays  and  crushing  blows  have 
inexperienced  persons  received  by  mistaking  some 
shining  substance  for  the  precious  metal,  and  only 
after  years  of  patient,  secret  keeping,  discovering  that 
"  all  is  not  gold  that  glitters." 

Comstock,  in  a  "  Treatise  on  the  Precious  Metals," 
relates  the  story  of  an  honest  farmer,  who  through 
long  years  preserved  the  secret  of  a  supposed  gold 
mine  of  inestimable  value,  which,  when  he  was  about 
to  reward  himself  for  his  patience,  turned  out  to  be 
nothing  but  fool's  gold  or  sulphuret  of  iron. 

Another  man,  of  a  somewhat  speculative  turn  of 
mind,  once  brought  a  specimen,  as  the  story  runs,  of 
a  supposed  very  rich  gold  ore  to  a  San  Francisco  as- 
sayer.  The  man  on  being  informed  that  it  was  noth- 
ing but  iron  pyrites,  and  not  worth  a  cent  a  ton,  ex- 


128 


INTEODUCTION. 


claimed,  in  the  most  extreme  dismay:  "Great  heav- 
ens !  there  is  an  old  woman  np  our  way  who  owns  a 
hill  of  it,  and  I  married  her !" 

The  greater  part  of  the  chapters  have  been  compiled 
from  that  incomparable  work  "Muspratt's  Chemistry," 
and  the  editor  has  tried  to  make  it  a  thoroughly  prac- 
tical treatise  and  one  which  the  most  unsophisticated 
can  understand. 

THE  AUTHOR. 

Brooklyn,  N.  Y.,  May,  1867. 


THE 

GOLD  WORKER'S  GUIDE. 


CHAPTER  I. 

SOURCES    OF    GOLD,  ETC. 

More  gold  is  now  produced  in  the  vast  continent  of 
North  America  than  in  any  other  part  of  the  world. 
In  this  respect  it  has  now  taken  the  place  which  form- 
erly belonged  to  South  America,  while  the  latter  has 
sunk  into  comparative  improductiveness,  less  perhaps 
from  the  absolute  exhaustion  of  the  auriferous  soils, 
than  from  the  want  of  the  capital  and  enterprise  to 
work  them  successfully.  North  America  was  a  gold- 
producing  continent  long  before  the  discovery  of  the 
Calif ornian  treasures;  but  for  many  years,  the  only 
source  of  this  precious  metal  in  that  quarter  of  the 
globe  was  the  argentiferous  veins  of  Mexico,  from 
which  it  was  extracted  along  with  the  silver,  as  in  the 
Peru  mines  of  South  America.  At  a  later  period, 
however,  an  extensive  gold  region  was  discovered  in 
the  United  States,  extending  along  the  Eastern  slope 
of  the  Appalachian  mountains,  from  the  River  Rappa- 
hannock in  Virginia  Southward  to  the  River  Coosa, 
an  affluent  to  the  Alabama,  which  flows  into  the  Gulf 
of  Mexico,  The  metal  is  found  in  less  quantity  North- 


130 


THE  GOLD  WOBKER's  GUIDE. 


ward  along  the  same  mountainous  range  to  the  State 
of  Maine,  and  even  extending  into  Canada,  where  a 
search  for  profitable  workings  has  lately  been  prose- 
cuted with  some  vigor.  The  existence  of  spangles  and 
pepitas  of  gold,  in  several  rivers  of  the  East  of  Canada, 
has  been  fully  established;  and  at  the  Great  Exhibi- 
tion honorable  mention  was  made  of  the  Chaudiere 
Mining  Company,  who  exhibited  pepitas  of  native 
gold,  collected  in  the  washings  of  those  streams.  But 
the  States  of  Virginia,  North  and  South  Carolina,  and 
Georgia,  afford  the  most  productive  deposits.  In  these, 
as  in  those  of  Brazil  and  Columbia,  the  auriferous  ores 
are  chiefly  pyritical;  much  of  the  gold  is  extracted  by 
amalgamation,  after  stamping  under  water. 

But  all  preceding  gold  discoveries  in  America,  or 
in  any  other  part  of  the  world,  were  eclipsed  by  those 
that  have  been  made  within  the  past  few  years  in 
California  and  Australia.  These  recent  discoveries 
have  produced  quite  a  revolution  in  the  annual  pro- 
duction of  gold,  the  effects  of  which,  though  already 
powerfully  felt  in  the  new  impulse  given  to  emigration 
and  commerce,  are  only  beginning  to  be  developed, 
and  must  produce  the  most  important  results  in  the 
future  history  of  the  world.  This  may  be  inferred 
from  the  fact,  that  the  gatherings  of  the  precious 
metal,  reckoning  the  average  produce  of  all  parts  of 
the  new  and  old  world  for  a  series  of  years  previous 
to  184:7,  did  not  amount  to  the  annual  value  of  five 
millions  sterling,  whereas  the  amount  now  exceeds 
thirty  millions  per  annum. 

The  first  of  these  recent  discoveries  was  made  in 
1847,  when  California,  a  hitherto-neglected  and  little- 


THE  GOLD  worker's  GUIDE. 


131 


known  region,  lying  at  the  most  remote  South-western 
limit  of  North  America,  rose  into  sudden  importance, 
as  the  El  Dorado  of  the  new  world.  The  gold  region, 
properly  so  called,  occupies  the  Northern  part  of  Cali- 
fornia, commencing  near  the  mouth  of  the  Sacramento 
Eiver,  in  latitude  39^  North,  and  longitude  1221° 
West,  to  the  North-east  of  the  bay  and  town  of  San 
Francisco,  from  which  it  extends  South  and  'North. 
At  this  point  two  rivers  unite  and  discharge  them- 
selves into  the  sea — the  Sacramento  flowing  from  the 
North,  along  a  valley  formed  by  mountain  ranges,  and 
the  San  Joaquim,  flowing  from  the  South,  along  a 
similar  valley,  enclosed  on  one  side  by  the  Eocky 
Mountains,  and  on  the  other  by  the  mountainous 
ridge  which  protects  the  Western  coast.  It  was  on 
the  property  of  an  intelligent  Swiss  emigrant.  Captain 
Suter,  who  had  become  a  wealthy  settler  on  the  banks 
of  the  Sacramento,  that  the  first  traces  of  gold  were 
discovered  in  September,  1847.  This  happened  in  the 
course  of  the  erection  of  saw-mills  on  the  estate,  when 
Mr.  Marshall,  the  contractor  for  the  building  of  these, 
observed  glitering  particles  in  the  sand  of  the  mill- 
race,  which  were  ascertained  to  be  gold;  and  on  mak- 
ing further  researches,  it  was  found  that  the  precious 
metal  was  very  extensively  diffused  in  the  bed  of  the 
stream.  The  discovery  soon  became  known  to  the 
work-people,  by  whom  the  intelligence  was  conveyed 
to  San  Francisco,  and  in  no  long  time,  the  whole  pop- 
ulation of  the  little  town,  and  the  scattered  and  scanty 
settlers  in  the  neighborhood,  abandoned  their  dwell- 
ings and  occupations  to  engage  in  the  exciting  search. 
The  supply  exceeded,  the  most  exaggerated  accounts 


132 


THE  GOLD  WOKKEr's  GUIDE. 


that  liad  been  given;  new  and  rictier  localities  were 
discovered;  tlie  gold  was  found  in  the  beds  of  various 
streams  flowing  into  the  Sacramento ;  in  the  mud  of 
the  river  itself;  in  the  channels  of  old  water-courses, 
and  along  the  sides  of  the  hills.  The  intelligence 
rapidly  spread  to  the  neighboring  countries — to  Mex- 
ico, to  South  America,  to  the  United  States,  and  thence 
to  Europe.  People  began  to  flock  from  all  quarters  to 
the  once  neglected,  but  now  coveted  region;  it  became, 
in  a  few  short  months,  the  scene  of  a  considerable  pop- 
ulation, instead  of  a  few  scattered  tribes  of  Indians; 
miners  or  diggers  in  parties  spread  themselves  over 
the  face  of  the  country;  and  San  Francisco,  from  a 
mere  village,  grew  up  into  a  place  of  wealth,  import- 
ance, and  stirring  activity.  It  was  at  first  very  gener- 
ally thought  that  the  supply  would  soon  fail,  but  this 
anticipation  has  proved  to  be  unfounded;  and  while, 
on  the  one  hand,  the  amount  of  the  precious  metal 
disseminated  in  the  rocks  and  soil  appears  to  be  al- 
most inexhaustible — on  the  other  hand,  the  constant 
increase  in  the  number  of  miners,  combined  with  the 
improved  apparatus  and  methods  of  working,  seems  to 
have  hitherto  resulted  in  a  steadily  increasing  annual 
produce,  until  within  the  last  few  years,  when  it  seems 
to  have  been  nearly  stationary. 

Professor  Blake,  who  minutely  examined  the  aurif- 
erous regions  of  California,  states  that,  with  the  excep- 
tion of  the  diluvial  strata,  the  whole  geological  forma- 
tion of  the  Sierra  range,  through  which  flow  the  prin- 
cipal rivers,  consists  of  igneous  and  metamorphic  rocks. 
The  former  are  mostly  porphyritic  in  the  lower  hills, 
whilst  higher  up  trachytic  rocks  egce  most  frequently 


THE  GOLD  worker's  GUIDE. 


133 


met  with.  The  metamorphic  rocks  consist  of  mica- 
ceous schists,  slates  both  talcose  and  micaceous,  meta- 
morphic sandstones  and  limestones,  with  occasional 
beds  of  conglomerate.  In  that  part  of  the  country 
which  he  examined,  the  extent  of  the  diluvial  deposits 
was  commensurate,  or  nearly  so,  with  that  of  the  gold- 
bearing  region.  They  are  found  in  a  belt  of  land  from 
thirty  to  sixty  miles  broad,  and  running  parallel  with 
the  axis  of  the  range.  These  diluvial  deposits  are  met 
with  toward  the  lower  hills  of  the  Sierra,  extending 
frequently  some  miles  into  the  plain.  The  elements 
of  which  they  are  composed  differ  considerably  in 
various  localities,  although  there  are  many  points  of 
resemblance  through  the  whole  series.  In  the  lower 
valleys  and  flats,  between  the  ranges  of  the  lower  hills, 
they  appear  to  consist  of  beds  of  gravel,  containing  oc- 
casional boulders  of  quartz  and  the  harder  rocks.  On 
the  elevated  flats,  higher  up  in  the  mountains,  the  sur- 
face of  these  deposits  is  generally  covered  by  a  reddish 
loam,  mixed  with  small  gravel;  whilst,  reposing  on  the 
bed  rock,  and  a  few  inches  above  it,  is  found  a  stratum 
containing  large  boulders  and  gravel,  the  boulders 
being  principally  quartz.  At  other  points,  the  whole 
series  consists  of  conglomerates  and  soft  friable  sand- 
stone. Where  the  deposits  are  found  extending  over 
a  large  surface  on  the  elevated  flats,  gold  is  always  met 
with,  generally  diffused  through  the  gravel  immediately 
above  the  rock  on  which  they  rest,  which  yields  from 
fifteen  to  forty  cents  to  the  hundred  pounds  of  earth. 
There  are  parts  where  acres  of  these  deposits  have 
been  turned  up,  in  which  the  gravel  never  contains  less 
than  fifteen  cents  to  the  hundred  pounds,  and  gener- 
6 


134 


THE  GOLD  worker's  GUIDE. 


ally  more.  In  the  valleys  in  the  lower  hills,  and  even 
on  the  plains  to  the  west  of  them,  where  they  are  ex- 
tended over  vast  tracts  of  country,  these  deposits  are 
stiU  auriferous,  the  gold  being  very  generally  diffused, 
and  found  in  greater  quantities  the  deeper  they  are 
worked  ;  but  sometimes  they  will  not  pay  for  working, 
owing  to  the  distance  from  water.  Iia  one  place  where 
water  could  be  readily  obtained,  a  portion  of  these 
deposits,  situated  to  the  west  of  the  lower  hills,  was 
found  to  yield  from  five  to  thirty  cents  to  one  hund- 
red pounds  of  earth,  through  an  extent  of  one 
hundred  and  fifty  acres,  the  soil  being  found  richer 
the  deeper  it  was  worked. 

At  a  spot  which  was  appropriately  named  Mount 
Ophir,  the  auriferous  soil  was  described  as  soft  clay 
and  slate,  saturated  with  gold  in  small  particles  and 
large  lumps.  This  treasure  was  found  from  ten  to 
thirty  feet  below  the  surface,  and  seven  Mexicans  who 
made  the  discovery,  and  kept  their  secret  eight  days, 
made  in  that  short  time  two  hundred  and  seventeen 
thousand  dollars. 

Other  searchers,  from  a  shaft  twenty  feet  deep, 
obtained  the  soft  clayey  slate  in  buckets,  and  found 
from  eight  to  twelve  dollars'  worth  in  each  bucket. 
In  many  cases  considerable  nuggets  are  met  with,  but 
no  accounts  speak  of  very  large  masses  of  gold  having 
been  found  in  California.  The  total  produce  from 
this  region,  down  to  the  end  of  1855,  was  estimated  at 
sixty-four  million  pounds  sterling ;  and,  latterly, 
it  has  averaged  about  fourteen  million  pounds  per 
annum. 


THE  GOLD  WOEKEr's  GUIDE 


135 


METHOD  OF  EXAMINING  AURIFEHOUS  DEPOSITS. 

As  a  general  rule,  the  rocks  in  the  district  to  be  ex- 
amined for  gold,  should  be  either  granitic,  porphyritic, 
or  quartzose,  although  it  is  found  in  other  formations, 
and  particularly  in  clay-slate.  The  auriferous  quartz 
is  often  stained  of  a  rusty  brown  color,  from  the  pres- 
ence of  peroxide  of  iron,  and  in  many  instances  pre- 
sents a  cellular  or  honeycombed  appearance.  The 
points  to  be  most  carefully  examined  are  the  sands  of 
the  rivers  and  streams,  or  old  water-courses,  as  well 
as  the  particles  of  disintegrated  rock  which  often  ac- 
cumulate in  the  eddies  of  ravines  formed  on  the  sides 
of  hills  by  the  action  of  water  during  great  floods. 
The  sections  of  rock  exposed  by  this  action  must  also 
be  examined  with  a  view  to  the  discovery  of  veins  of 
auriferous  quartz,  from  which  fragments  are  broken 
off  and  afterwards  carefully  assayed. 

The  method  of  conducting  a  systematic  assay  of 
gold  ores  and  alloys  will  be  fully  explained  afterwards. 
It  is  a  somewhat  tedious  and  difficult  process,  requir- 
ing considerable  experience  and  a  regular  assortment 
of  apparatus.  But  even  in  the  absence  of  these,  a  tol- 
erably correct  estimate  of  the  amount  of  gold  present, 
may  be  readily  arrived  at  by  the  following  simple 
method. 

The  fragment  of  rock,  supposing  the  ore  to  be 
quartz,  is  first  pounded  very  fine  and  sifted,  a  portion 
of  the  sand  or  powder  thus  obtained  is  washed  in  a 
shallow  pan,  and,  as  the  gold  sinks,  the  lighter  por- 
tions of  the  substance  are  allowed  to  float  off.  The 
greater  part  of  the  gold  is  thus  left  in  the  angles  of 


136 


THE  GOLD  worker's  GUIDE. 


the  pan  ;  and  by  adding  more  of  the  powder,  and  re- 
peating the  same  process,  a  further  portion  is  ob- 
tained. When  the  bulk  of  powder,  with  which  the 
gold  is  mixed,  is  thus  reduced  to  a  manageable  quan- 
tity, mercury  is  added  to  the  mass,  and  forms  with 
the  gold  an  amalgam,  which  is  afterwards  heated  in 
an  iron  retort,  to  expel  the  mercury.  In  this  way  the 
proportion  of  gold  contained  in  a  specimen  of  rock 
may  be  ascertained  with  considerable  exactness.  The 
sands  brought  down  by  rivers  are  examined  in  much 
the  same  manner,  but  do  not  require  the  previous 
pounding  ;  and  a  fair  estimate  of  their  value  may  be 
generally  formed  without  the  amalgamating  process. 
Sometimes,  indeed,  the  gold  may  be  present  in  con- 
siderable quantity,  although  in  a  state  of  division  so 
minute  as  not  to  be  readily  perceived  by  the  un- 
assisted eye,  and,  therefore,  in  examining  the  earthy 
residuum,  a  small  magnifying  lens  will  be  found  of 
great  use. 

It  is  generally  conceded  that  the  sand  of  any  river 
is  worth  working  for  the  gold  it  contains,  provided  it 
will  yield  twenty-four  grains  to  the  hundred  weight; 
but  the  sands  of  the  African  rivers  often  yield  sixty 
grains  in  not  more  than  five  pounds  weight,  which  is 
in  the  proportion  of  more  than  fifty  times  as  much, 
while  the  Australian  rivers  have  been  known  to  yield 
considerably  more. 

SUBSTANCES  OFTEN  MISTAKEN  FOR  GOLD. 

Though  gold,  in  its  separate  and  pure  state,  is  read- 
ily distinguishable  from  other  metals  and  minerals,  by 
its  color,  softness,  and  high  specific  gravity,  and  in- 


THE  GOLD  WOBKEr's  GUIDE. 


137 


solubility  in  the  simple  acids,  yet  in  the  mixed  state 
in  which  it  is  generally  found,  it  requires  an  amount 
of  chemical  skill  to  apply  these  tests,  and  hence, 
where  glittering  particles  of  other  minerals  appear, 
they  are  often  mistaken  for  gold,  even  by  persons  who 
are  not  entirely  ignorant  of  its  characteristics.  The 
substances  which  most  genelrally  lead  to  this  mistake 
are  iron  pyrites,  copper  pyrites  and  yellow  mica. 

Common  iron  pyrites,  or  bisulphide  of  iron,  which  is 
more  frequently  mistaken  for  gold  than  any  other  sub- 
stance, occurs  in  small  cubical  crystals,  in  veins  dis- 
semminated  in  the  various  slate  rocks,  and  in  the  coal 
measures.  It  is  of  different  shades  of  brass-yellow, 
and  often  in  fact  contains  minute  traces  of  gold,  though 
seldom  a  sufficient  amount  of  that  metal  to  render  its 
extraction  profitable.  It  may  be  readily  distinguished 
from  gold  by  the  application  of  the  magnet,  as  well  as 
by  the  following  characters  :  first,  instead  of  flattening 
like  gold  under  the  hammer,  it  is  extremely  brittle,  and, 
therefore,  readily  broken ;  second,  its  weight  or  specific 
gravity  is  only  about  one-fourth  that  of  gold ;  and, 
lastly,  when  heated  with  nitric  acid  it  is  dissolved  with 
evolution  of  copious  red  fumes,  whilst  gold,  when  so 
treated,  remains  unaffected.  It  was  only  recently  the 
Editor  was  consulted  by  a  gentleman  who  imagined 
he  had  discovered  a  gold  mine  in  Ireland.  The  sample 
brought  turned  out  to  be  a  fine  specimen  of  sulphide 
of  iron  embedded  in  quartz. 

Copper  pyrites,  or  yellow  copper  ore,  the  second 
mineral  which  is  frequently  mistaken  for  gold,  is  a 
ferrosulphide  of  copper,  and  may  be  considered  as  a 
compound  of  two  equivalents  of  sulphide  of  iron,  and 


138 


THE  GOLD  worker's  GUIDE. 


one  equivalent  of  sulphide  of  copper.  This  is  the  ore 
from  which  the  largest  proportion  of  the  copper  of  com- 
merce is  derived.  It  occurs  in  a  variety  of  forms,  its 
primitive  crystal  being  the  regular  tetrahedron.  It  is 
formed  in  lodes  or  veins,  which  usually  occur  either  in 
granite,  grauwacke,  or  clay-slate,  and  has  a  strong 
metallic  lustre,  and  deep  brass-yellow  color.  It  may 
readily  be  distinguished  from  gold  by  the  circumstance, 
that  when  heated  on  a  piece  of  charcoal  before  the 
blow-pipe  it  loses  this  yellow  color  and  fuses  into  a  dull 
black  globule  which,  from  the  presence  of  the  iron,  is 
magnetic.  If  mixed  with  corbonate  of  soda  and  a  little 
borax,  it  yields,  when  similarly  treated,  in  skillful 
hands,  a  button  of  metallic  copper.  But  an  easier 
method  to  determine  the  presence  of  copper  is  to  pul- 
verize the  ore  in  an  iron  mortar,  or  with  a  heavy  ham- 
mer, dissolving  the  powder  thus  obtained  into  nitric 
acid,  and  evaporating  the  solution  nearly  to  dryness  ; 
water  is  then  added,  and  afterward  ammonia  in  ex- 
cess, when,  if  copper  be  present,  the  liquor  assumes  a 
rich  purplish  color,  an  unmistakeable  sign  of  the  pres- 
ence of  copper. 

Another  method  for  determining  the  presence  both 
of  iron  and  copper,  is  to  take  some  of  the  scoria  left 
after  putting  this  in  a  blowpipe,  and,  putting  this  in  a 
test-glass,  to  pour  over  it  a  few  drops  of  hydrochloric 
acid,  when  an  effervescing  solution  will  be  obtained. 
A  little  of  this  liquid  is  then  transferred  to  another 
glass — the  one  to  be  treated  for  iron,  the  other  for 
copper.  Into  one  of  the  glasses  introduce  a  few  drops 
of  ferro-cyanide  of  potassium,  and  liquid  ammonia 
into  the  other.    If  iron  is  present,  the  liquid  in  the 


THE  GOLD  WOHKER's  GUIDE 


139 


glass  to  which  the  ferro-cyanide  has  been  added  will 
become  blue,  the  iron  combining  with  the  ferro- 
cyanogen,  and  producing  Prussian  blue.  If  copper  is 
present  in  the  same  glass,  but  no  iron,  the  liquid  will 
become  of  a  reddish-brown  tint,  ferro-cyanide  of  cop- 
per being  formed.  If  iron  and  copper  are  present  to- 
gether, the  two  metallic  precipitates  will  be  the  result, 
and  a  purple  tint  arises  from  the  mixing  of  the  red 
and  blue  colors.  The  liquid  in  the  glass  to  which  am- 
monia was  added  will  be  changed  to  a  brownish 
tint  if  iron  is  present,  and  to  a  fine  blue  if  copper  is 
there. 

Mica^  the  third  substance  often  mistaken  for 
gold,  is  one  of  the  constituents  of  gneiss,  granite, 
and  mica  slate,  and  gives  to  the  former  its  lamellar 
structure. 

The  specific  gravity  of  mica  never  exceeds  3'00;  and 
this  circumstance,  together  with  its  foliated  structure, 
is  quite  sufficient  to  distinguish  it  from  gold,  which 
it  somewhat  resembles  in  color;  but  even  in  this 
latter  particular  the  microscope  will  dispel  the  il- 
lusion. 

CHARACTERS  OF  NATIVE  GOLD. 

Gold,  as  already  stated,  almost  always  occurs  in  the 
metallic  state,  generally  in  small  grains  or  scales 
known  as  gold  dust,  sometimes  in  particles  so  minute 
as  to  be  invisible,  but  occasionally  in  pieces  of  con- 
siderable weight,  termed  nuggets.  It  appears  doubt- 
ful, indeed,  whether,  when  this  metal  occurs  in  pyrites, 
it  exists  in  every  instance  in  metallic  particles,  or 
whether,  in  some  cases  at  least,  it  may  not  be  present 


140 


THE  GOLD  WOEKEr's  GUIDE. 


in  combination  with  sulphur.  The  auriferous  pyrites, 
as  Dumas  remarks,  contain  the  gold  disseminated 
through  their  mass  in  such  small  quantities,  that  it  is 
almost  always  impossible  to  ascertain,  even  with  the 
aid  of  the  microscope,  in  what  state  the  precious  metal 
exists.  As  a  preliminary  roasting  of  this  auriferous 
ore  is  generally  useful,  with  a  view  to  the  subsequent 
amalgamation,  a  doubt  may  be  entertained  whether  it 
is  really  present  in  the  metallic  state,  though  this  has 
been  generally  assumed  hitherto.  But  Dumas  thinks 
that  the  powerful  electro-negative  tendency  of  sul- 
phide of  gold  affords  a  strong  presumption  in  favor  of 
the  hypothesis,  that  this  metal  may  exist  partly,  or 
even  entirely,  under  the  form  of  a  double  sulphide,  in 
iron  and  copper  pyrites,  et  cetera.  Brogniart  ob- 
serves, that  ^it  is  chiefly  in  its  association  with  those 
sulphides,  as  also  with  galena  or  sulphide  of  lead, 
blende,  or  sulphide  of  zinc,  and  mispicked  or  arsenical 
pyrites — a  sulphide  of  arsenic  and  iron — that  the  gold 
becomes  invisible  to  the  eye,  a  circumstance  which  is 
justly  regarded  as  strongly  confirming  the  opinion  ex- 
pressed by  Dumas.  The  other  minerals  with  which  it 
is  found  associated  are  grey  cobalt,  lithoidal  manga- 
nese, native  tellurium,  malachite,  sulphide  of  silver, 
red  silver  and  sulphide  of  antimony. 

COMPOSITION  OF  NATIVE  GOLD. 

Native  gold  is  never  quite  pure,  being  almost  invari- 
ably alloyed  with  silver,  and  containing  frequently 
small  portions  of  copper  and  iron.  In  Siberia  it  is 
often  associated  with  platinum,  and  in  the  Gongo 
Soco  mines  in  Brazil,  an  alloy  of  gold  and  palladium 


THE  GOLD  WOKKER's  GUIDE. 


141 


of  a  pale  yellow  color  is  sometimes  found.  In  Colum- 
bia a  somewhat  similar  mixture  is  procured,  in  which 
the  palladium  is  replaced  by  another  rare  metal  called 
rhodium.  In  Hungary  it  is  met  with  in  combination 
with  tellurium  and  other  elements.  The  specific 
gravity  of  native  gold  varies  from  13*3  to  18*5. 

The  proportion  of  silver,  the  principal  ingredient 
which  is  found  in  combination  with  gold,  varies  from 
one  to  fifty  per  cent.,  and  not  only  differs  greatly  in 
specimens  of  native  gold  obtained  from  diverse  regions, 
but  even  to  a  certain  extent  in  specimens  from  the 
same  auriferous  district.  In  general,  however,  the 
composition  of  the  gold  of  the  same  district  is  remark- 
ably constant;  so  much  so  that  the  knowledge  of  the 
locality  whence  it  is  derived,  is  often  sufiicient  to  en- 
able the  experienced  assayist  to  guess  pretty  nearly 
the  quantity  of  pure  gold  which  the  compound  contains. 
The  subjoined  table  presents  the  composition  of  native 
gold  from  various  parts  of  the  world  : 


6^ 


142  THE  GOLD  WOEKEr's  GUIDE. 


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THE  GOLD  worker's  GUIDE. 


143 


From  this  table  it  will  be  seen  that  the  gold  both  of 
California  and  Australia  contains  silver,  but  that  the 
specimen  from  the  latter  was  remarkably  pure ;  and 
such,  indeed,  is  the  general  character  of  Australian 
gold.  Neither  platinum  nor  palladium,  nor  any  trace 
of  the  metals  of  that  class  is  found  in  the  newly 
discovered  gold  regions.  There  is,  however,  a 
trace  of  iron  in  the  Australian  specimen  and  a  small 
proportion  of  both  copper  and  iron  in  those  from  Cali- 
fornia. 

PROPERTIES  OF  PURE  GOLD. 

Pure  gold  is  of  a  rich  reddish-yellow  color  and  high 
metallic  luster ;  in  the  pulverulent  state  it  is  brown 
and  dull,  but  acquires,  as  has  been  stated,  the  metallic 
luster  by  pressure.  The  specific  gravity  of  fused  gold 
is  19*2  ;  of  hammered  gold  from  19*3  to  19*4.  In  this 
respect,  therefore,  it  stands  second  only  to  platinum, 
of  which  the  specific  gravity  is  about  21*5.  Finely  di- 
vided gold,  precipitated  by  sulphate  of  iron,  was  found 
to  vary  in  density  from  19*55  to  20*72;  and  when  X3re- 
cipitated  by  oxalic  acid  its  density  was  19*49.  Its 
equivalent  is  197.  In  a  pure  state  it  is  softer  than 
silver  and  nearly  as  soft  as  lead;  but  its  tenacity  is  so 
great  that  it  may  be  drawn  out  into  very  fine  wire; 
and  such  is  its  malleability  that  it  may  be  hammered 
out  into  leaves  only  one  three  hundred  and  seventy 
thousandth  of  an  inch  in  thickness.  A  single  grain 
may  be  extended  over  56*75  square  inches  of  surface, 
or  drawn  out  into  a  wire  five  hundred  feet  long. 
Keamur,  by  rolling  out  a  fine  gilt  silver  wire,  reduced 
the  coating  of  gold  to  the  twelve  millionth  of  an  inch 


THE  GOLD  worker's  GUIDE. 


in  thickness,  and  the  surface  appeared  to  be  perfect 
"when  viewed  under  the  microscope. 

Gold  does  not  combine  directly  with  oxygen,  and, 
therefore,  suffers  no  change  by  exposure  to  air  and 
moisture  at  any  temperature — not  even  by  being  kept 
in  a  state  of  fusion  in  open  vessels.  It  is  not  attacked 
by  the  mineral,  or  any  of  the  simple  acids,  except  se- 
lenic,  and  this  by  the  aid  of  heat.  The  alkalies  do  not 
affect  it,  and  hence  a  crucible  of  gold  is  a  valuable  in- 
strument in  the  analysis  of  minerals  which  require 
fusion  with  the  caustic  alkalies.  It  is  not  acted  on  by 
sulphur  and,  consequently,  sulphide  of  hydrogen  is  not 
decomposed  by  it,  as  in  the  case  of  silver.  Iodine  has 
only  a  weak  action  upon  it,  but  bromine  and  chlorine 
attack  it  easily  at  ordinary  temperatures;  and  it  is  dis- 
solved by  any  substance  which  liberates  chlorine.  It 
is  therefore  dissolved  by  hydrochloric  acid,  if  binoxide 
of  maganese,  chromic  acid,  etc.,  be  added  thereto.  Its 
usual  solvent  is  that  already  stated — a  mixture  of  one 
part  of  nitric  acid  and  four  parts  of  hydrochloric  acid. 
The  proper  solvent  of  gold  is  nascent  chlorine,  which  is 
eliminated  by  the  mutual  action  of  the  mixed  acids. 

Gold  is  one  of  the  most  perfect  conductors,  both  of 
heat  and  electricity.  It  fuses  at  a  bright  red  or  a 
white  heat,  the  temperature  of  which  has  been  esti- 
mated at  2016^  Fahr.  It  is  therefore  less  fusible  than 
silver  or  copper,  the  former  fusing  at  1873^,  and  the 
latter  at  1996^.  In  fusion  it  exhibits  a  bluish-green 
color.  It  is  not  sensibly  volatile  in  the  strongest  heat 
of  a  blast  furnace;  but  in  the  focus  of  a  large  convex 
lens,  in  the  intense  heat  of  the  oxyhydrogen  jet,  or 
under  the  influence  of  a  powerful  electric  discharge,  a 


THE  GOLD  worker's  GUIDE. 


145 


gold  wire  is  dispersed  in  vapor;  and  if,  in  the  latter 
case,  the  wire  be  placed  just  above  the  surface  of  a 
sheet  of  paper,  the  course  of  the  discharge  is  marked 
by  a  broad,  dark,  purple  stain,  produced  by  the  finely- 
divided  gold.  If,  instead  of  the  sheef  of  white  paper, 
a  plate  of  polished  silver  be  employed,  it  is  traversed 
by  a  brightly-gilded  line,  which  is  firmly  attached  to 
its  surface.  When  a  globule  of  gold  is  placed  between 
the  terminal  charcoal  points  of  a  powerful  voltaic  bat- 
tery, it  enters  almost  into  fusion,  and  gives  off  abund- 
ant metallic  fumes. 

Gold  contracts  on  cooling,  and  cannot  be  advanta- 
geously employed  for  castings,  as  it  shrinks  greatly  at 
the  moment  of  solidifying.  Graham  states  that  it 
cannot  be  obtained  in  crystals  by  cooling;  but  according 
to  other  authorities,  when  large  quantities  of  gold 
have  been  fused,  and  are  then  allowed  to  cool  slowly, 
cubes  more  or  less  modified  on  their  edges  and  angles 
are  frequently  the  result.  It  has  been  shown  that  na- 
tive gold  affords  numerous  well  defined  crystals  be- 
longing to  the  cubic  system,  and  that  of  these  the 
greaier  number,  if  not  all,  is  affected  by  the  faces  of 
the  regular  octahedron. 


*    CHAPTEE  II. 

CHEMICAL  EXAMINATION  OF    GOLD  ORES. 

A  RUDE  method  of  ascertaining  the  presence  of  gold 
in  crushed  quartz  or  earthy  ore,  by  washing  with  the 
hand-basin,  has  been  described;  but  gold  is  often  pres- 
ent in  the  matrix  in  grains  or  particles  so  minute  that 
it  cannot  be  detected  by  the  eye,  and  sometimes  it  is 
quite  disguised  by  admixture  with  other  metals  or 
minerals.  Many  cases  occur,  however,  in  which  it  is 
of  great  importance  to  ascertain  the  presence  of  gold, 
not  only  as  a  first  step  in  the  examination  of  suspected 
auriferous  ores,  but  likewise  in  the  assaying  of  alloys 
of  gold  with  different  metals.  In  commencing  mining 
operations,  the  fact  of  the  presence  of  gold  in  the  ore 
in  any  appreciable  quantity,  is  the  first  point  to  be  de- 
termined; and  if  this  be  decided  in  the  affirmative,  the 
next  point  is  to  determine  the  proportion  or  quantity  of 
gold  contained.  The  first  process  is  termed  testing  for 
gold,  or  the  qualitative  examination  of  a  suspected  min- 
eral; the  second  is  the  quantitative  examination,  or  as- 
saying  process. 

Sulphate  of  iron,  protochloride  of  tin,  and  oxalic 
acid  are  the  tests  or  reagents  pre-eminently  employed 
in  seeking  to  determine  the  presence  of  gold. 

Before  any  of  these  tests  can  be  applied,  the  sub- 
stance supposed  to  contain  the  gold  must  be  brought 


THE  GOLD  worker's  GUIDE. 


147 


into  a  state  of  solution;  and  this  can  only  be  done  by 
means  of  the  mixture  of  nitric  and  hydrochloric  acids 
already  mentioned.  If  the  substance  consist  of  earthy 
or  quartzose  matter,  this  must  be  reduced  to  powder 
by  trituration  in  a  mortar  before  it  is  subjected  to  the 
action  of  the  solvent;  but  if  the  matter  under  examina- 
tion be  simply  a  metallic  alloy,  it  can  be  dissolved 
without  any  previous  preparation.  An  excess  of  acid 
should  be  avoided,  and  for  this  purpose  some  carbonate 
of  soda  should  be  added.  When  the  solution  is  ef- 
fected, the  liquid  should  be  evaporated  to  about  one- 
eighth  of  its  original  bulk,  and  then  diluted  with  three 
or  four  ounces  of  water.  The  action  of  the  reagents  is 
as  follows: 

1.  Sulphate  of  Iron  or  Green  Vitriol. 

If  a  few  crystals  of  this  salt  be  dissolved  in  dis- 
tilled water,  and  dropped  into  the  suspected  solution, 
the  result  is  the  precipitation  of  the  gold  if  any  be 
present,  in  the  form  of  a  dark-brown  powder,  which  is 
metallic  gold  in  a  very  fine  state  of  division,  as  already 
described  in  connection  with  the  laboratory  process 
for  preparing  pure  gold.  If  the  solution  has  been 
mixed  with  a  considerable  quantity  of  water,  the 
liquid,  on  the  addition  of  the  green  vitriol,  is  colored 
brown  by  reflected,  and  blue  or  a  dingy  green,  by 
transmitted  light;  and  this  is  obvious  even  when  forty 
thousand  parts  of  the  menstruum  are  present  to  one 
part  of  gold.  If  the  liquid  amount  to  eighty  thousand 
parts  it  is  colored  sky-blue;  with  one  hundred  and 
sixty  thousand  parts  it  becomes  violet;  with  three 


148 


THE  GOLD  worker's  GUIDE. 


hundred  and  twenty  thousand  parts  of  liquid, 
the  violet  tint  is  still  very  obvious;  but  with  six 
hundred  and  forty  thousand  parts,  it  is  with  diflEiculty 
perceived. 

The  deposit  formed  when  sulphate  of  iron  is  added, 
may  be  corroboratively  proved  to  be  gold,  by  its  being 
insoluble  in  nitric  acid,  but  readily  soluble  in  aqua 
regia. 

2.  Frotochloride  of  Tin. 

If  to  another  portion  of  the  nitro-hydrochloric  so- 
lution be  added  a  small  quantity  of  a  solution  of  pro- 
tochloride  Qf  tin — commonly  known  as  salts  of  tin — 
there  will  be  immediately  produced,  if  any  gold  is 
present,  a  dark  brownish-purple  precipitate  known  as 
purple  of  Cassius,  This  substance  is  used  in  enamel 
and  porcelain  painting,  and  also  for  tinging  glass  of  a 
fine  red  color,  in  connection  with  which  applications 
it  will  be  noticed  afterwards.  Its  color,  though  not  a 
brilliant  purple,  but  rather  a  reddish-brown,  is  charac- 
teristic, and  after  being  once  seen  is  not  Ukely  to  be 
mistaken.  Its  appearance,  when  the  chloride  of  tin  is 
added  to  the  liquid,  affords  an  infaUible  proof  of  the 
presence  of  gold,  for  a  very  minute  portion  of  that 
metal  gives  a  manifest  reaction  when  this  test  is 
employed. 

When  the  first  test — sulphate  of  iron — has  been  ap- 
plied, and  its  evidence  corroborated  by  the  solution  of 
the  precipitated  gold  powder  in  aqua  regia,  the  proto- 
chloride  of  tin  may  be  employed  to  produce  the  purple 
of  Cassius  in  this  solution  also. 


THE  GOLD  worker's  GUIDE. 


149 


3.  Oxalic  Acid, 

This  substance,  either  in  crystals,  Or  dissolved  in 
water,  causes,  when  added  to  the  nitro-hydrochloric 
solution,  the  precipitation  of  any  gold  that  may  be 
present,  in  the  form  of  a  brown  or  greenish-black 
powder,  in  the  same  manner  as  the  sulphate  of  iron; 
but  the  precipitation  does  not  occur  so  rapidly.  In- 
deed, it  requires  not  less  than  forty-eight  hours  for  the 
whole  of  the  gold  to  be  thrown  down  by  the  oxalic 
acid,  unless  heat  is  applied,  by  which  the  process  is 
accelerated.  The  precipitate  is  pulverulent  gold,  and 
may  be  tested,  as  in  the  first  case,  by  its  insolubility 
in  nitric  acid,  while  readily  dissolving  in  aqua  regia. 
A  crystal  of  oxalic  acid,  wetted  with  a  solution  of 
gold,  becomes  soon  covered  with  a  thin  film  of  the 
metal,  having  its  distinctive  color  and  luster. 

These  are  the  tests  most  easily  employed  by  persons 
unaccustomed  to  chemical  manipulation.  At  the 
same  time,  it  may  be  useful  to  know  the  reactions  of 
gold  with  various  other  substances,  the  most  impor- 
tant of  which,  including  the  three  already  mentioned, 
are  summarily  tabulated  as  follows  by  Dr.  Lyon  Play- 
fair,  in  a  lecture  delivered  by  that  chemist  at  the  Mu- 
seum of  Practical  Geology: 

TESTS  FOR  GOLD. 


Tests  or  reagents. 
Sulphate  of  iron, 

Protochloride  of  Tin, 


Results. 

In  acid  solution,  brown  precipi- 
tate; if  very  dilute  solution, 
only  a  blue  coloring. 

In  dilute  solution,  a  purple-red 
coloring;  when  strong,  al- 
most brown  precipitate. 


150 


THE  GOLD  worker's  GUIDE. 


Tests  or  Keagents.  Kesults. 

( Precipitates  metallic  gold  as  a 
Metallic  zinc,  .      .      .      A    voluminous  brown  precipi- 

(  tate. 

'  No  precipitate ;  after  some  time 


Potassa  in  excess,    .      .      .  -<     a  green  coloring  and  slight 

(  precipitate. 

A^w.^«^c  5  Yellow   precipitate— fulminat- 

Ammonia,      .      .      .      .|  ^^il 

nate  o  pota^^^^^^^^  but  when  heated,  yolunainous 

xiatc     pwtaooa,  .J    precipitate  like  oxide  of  iron. 

Bicarbonates  of  soda  or  potassa  No  precipitate. 

r«o^i.^,.«f^     o^^^«,'«  (Behaves  like  ammonia,  car- 

Carbonate  of  ammonia,  .      .|    bonic  acid  being  evolved. 

C  Dark,  greenish-black  precipi- 
Oxalic  acid,     .      .      .      .  ■<    tate,  more  quickly  produced 

(    by  heat. 

Tartaric  acid  and  soda,  .      .   Dark  precipitate  when  boiled. 

Sulphide  of  ammonium  and  j  Dark  brown  or  black  precipi- 
Sulphide  of  hydrogen,  .      .  {  tate. 

These  reactions  are  so  characteristic  that  it  is  im- 
possible to  mistake  gold  for  any  other  metal.  At  the 
same  time  it  may  be  stated  that  the  protochloride  of 
tin  is  the  most  infallible  test,  and  is  indeed  quite  con- 
clusive. It  has  the  advantage  of  being  more  delicate 
than  the  others — that  is  to  say,  it  will  indicate  tlie 
presence  of  a  smaller  quantity  of  gold  than  any  other 
reagent,  not  excepting  the  protosulphate  of  iron  or 
the  oxalic  acid. 

TEST  FOR  METALS  USUALLY  ASSOCIATED  WITH  GOLD. 

In  examining  an  ore  or  alloy  supposed  to  contain 
gold,  it  is  often  an  object  of  great  importance  to  de- 
termine the  nature  of  the  metals  with  which  the  gold 
is  associated.  These  may  be  of  high  value  on  their 
own  account,  and,  according  to   the  quantities  in 


THE  GOLD  WOKKEr's  GUIDE. 


151 


wliicli  they  are  present,  may  greatly  affect  the  value  of 
the  ore  or  mineral  in  question.  To  enter  fully  into 
this  subject  in  connection  with  the  rarer  metals  that 
are  found  associated  with  gold,  would  be  of  little  prac- 
tical use.  The  Editor  will  therefore  confine  his  atten- 
tion ta  the  means  of  detecting  and  distinguishing 
those  of  most  common  occurrence — copper,  silver,  and 
platinum. 

1. — Copper, 

It  has  been  shown  that  copper  is  almost  always  as- 
sociated with  gold,  even  in  quartz,  and  that  copper  py- 
rites is  one  of  those  substances  frequently  mistaken 
for  gold.  When  dissolved  in  acids,  however^  it  gives 
characteristic  actions,  which  render  its  presence  easily 
distinguishable.  One  of  the  readiest  tests  is  to  intro- 
duce into  the  solution  a  piece  of  clean  iron,  when,  if 
copper  be  present,  it  will  be  deposited  on  the  iron  in 
the  metallic  state.  This  experiment,  remarks  Dr.  Lyon 
Playfair,  apparently  showing  the  conversion  of  iron 
into  copper,  deceived  the  alchemists  in  their  re- 
searches, and  gave  much  support  to  the  idea  that  one 
metal  may  be  transmuted  into  another.  The  action, 
depends,  however,  upon  a  simple  exchange,  the  iron 
going  into  the  solution  in  proportion  as  the  copper 
goes  out.  Again,  when  ammonia  is  added  in  excess 
to  a  solution  in  which  copper  exists,  it  communicates 
to  the  liquid  a  rich  deep  blue  color.  Ferrocyanide  of 
potassium  produces,  with  copper,  a  brownish-red  pre- 
cipitate, even  when  the  metal  is  present  in  very  small 
quantity.  Carbonate  of  soda  precipitates  copper  from 
its  hot  solutions  in  the  form  of  an  apple-green  com- 


152 


THE  GOLD  worker's  GUIDE. 


pound,  wliicli  is  a  carbonate  of  copper  known,  when 
artificially  formed,  as  verditei^  and  when  it  occurs  na- 
tive, as  malachite.  Copper  ore  in  the  latter  form  exists 
abundantly  in  Australia — not,  indeed,  mixed  with  the 
gold,  but  constituting  valuable  mines,  from  which  the 
ore  is  sent  over  to  England,  with  great  iDrofit,  to  be 
smelted  in  South  Wales. 

2.  Silver. 

It  has  been  shown  that  gold  appears  to  be  invariably 
alloyed  with  this  metal,  sometimes  to  a  very  large 
amount.  In  its  separate  state  it  is  readily  distin- 
guished, not  only  by  its  white  color,  but  also  by  its 
specific  gravity,  which  is  only  10*4,  or  about  one-half 
that  of  gold.  It  may  be  useful  to  state,  that  when  in 
a  very  fine  state  of  division  it  is  of  a  dark  grey  color. 
It  may  be  easily  recognized  by  its  chemical  behavior 
to  reagents,  in  which  respect  it  differs  from  gold  by 
solubility  in  nitric  acid  at  all  temperatures,  and  in 
boiling  or  heated  sulphuric  acid.  On  the  contrary, 
with  hydrochloric  acid,  it  forms  a  white  curdy  precipi- 
tate, which  is  the  chloride  of  silver.  If  the  nitric  acid 
employed  to  dissolve  it  contain  the  least  hydrochloric 
acid,  the  solution  will  become  turbid  by  the  formation 
of  the  chloride.  Hence,  when  a  mineral  containing 
gold  and  silver  is  submitted  to  the  action  of  aqua  regia 
— nitro-hydrochloric  acid — ^the  appearance  of  this 
white  precipitate  will  immediately  indicate  the  pres- 
ence of  the  latter  metal.  The  chloride  of  silver  is 
soluble  in  ammonia,  and  may  thus  be  distinguished 
from  many  other  white  precipitates;  or  it  may  be  fur- 
ther tested  by  putting  the  precipitate  into  a  crucible 


THE  GOLD  WOKKEr's  GUIDE.  153 

with  carbonate  of  soda,  and  exposing  the  mixture  to  a 
strong  red  heat,  when  a  button  of  pure  silver  will  be 
obtained.  By  careful  manipulation  the  amount  of 
silver  present  may  be  accurately  determined  in  this 
manner.  If  the  mineral  containing  the  silver  be  dis- 
solved in  oil  of  vitriol,  it  is  readily  detected  by  insert- 
ing a  few  fragments  of  copper,  which  causes  the 
precipitation  of  the  silver  in  a  pulverulent  state. 

From  the  fact  that  silver,  in  greater  or  less  propor- 
tion, is  uniformly  associated  with  gold  in  the  native 
state,  it  may  be  useful  to  compare  the  following  reac- 
tions with  those  given  in  the  preceding  page,  for  the 
metal  of  higher  value : 


TESTS  FOB  SrLYEK. 


Tests  or  Eeagents. 

Potassa,  I 

Ammonia,       .      .      .      .  | 
Carbonate  of  soda  or  potassa,  | 
Carbonate  of  ammonia,  .      .  | 
Phosphate  of  soda,  . 
Oxalic  acid, 

Sulphide  of  hydrogen  and  sul 
phide  of  ammonium,  . 

Hydrochloric  acid,  .  "  . 
Zinc  or  copper, 
Sulphate  of  iron, 


Results. 

Brown    precipitate,  becomes 
blacli  on  boiUng. 

Brown  precipitate,  soluble  in 
excess  of  ammonia. 

White  precipitate,  soluble  in 
ammonia. 

White  precipitate,  soluble  in 
excess  of  reagent. 

[  Yellow  precipitate,  soluble  in 
[  ammonia. 

1  In  neutral  solutions,  white  pre- 
[  cipitate. 

-  Black  precipitate. 

;  White  curdy  precipitate,  solu- 
'    ble  in  ammonia. 


;  Precipitates  white  metallic 
[  silver. 

In  neutral  solutions,  white  me- 
tallic silver. 


154 


THE  GOLD  worker's  GUIDE. 


3.  Platinum, 

This  is  another  metal  frequently  associated  with 
gold;  and  as  it  is  one  of  the  noble  metals,  and  ranks  in 
price  between  silver  and  gold,  an  ore  which  contains  it 
in  any  considerable  quantity  is  of  great  value.  The 
specific  gravity  of  platinum  is  about  21*5,  and  is, 
therefore,  greater  than  that  of  gold.  In  short,  plati- 
num is  the  heaviest  of  all  known  substances.  It  is  of 
a  light  steel-grey  color,  less  ductile  than  gold  or  silver, 
but  more  tenacious,  and  will  support  greater  weights 
on  equal  thicknesses  of  wire  than  any  metal  except 
iron  or  copper.  It  is  distinguished  from  gold  not  only 
by  its  color  but  also  by  its  extreme  difficulty  of  fusion; 
it  does  not  melt  by  itself  in  the  highest  heat  of  a  fur- 
nace, but  softens  sufficiently  to  admit  of  forging  and 
welding,  and  in  the  arc  of  flame  of  the  voltaic  current, 
or  before  the  oxyhydrogen  blowpipe,  it  admits  of  being 
fused  in  considerable  masses.  On  the  other  hand,  it 
resembles  gold,  not  only  in  its  high  specific  gravit}^, 
as  already  stated,  but  also  in  the  fact  that  it  resists  the 
action  of  all  the  simple  acids,  and  is  soluble  only  in 
aqua  regia.  This  circumstance,  together  with  its 
great  infusibility,  renders  it  importantly  useful  in 
many  of  the  arts  and  indispensable  for  various  pur- 
poses in  the  chemical  laboratory.  It  is  the  metal  uni- 
versally employed  for  apparatus  which  requires  to  be 
exposed  to  high  temperature  and  powerful  chemical 
agencies,  without  undergoing  any  change.  It  is,  there- 
fore, very  desirable,  as  Dr.  Lyon  Playfair  has  re- 
marked, that  those  who  go  to  the  gold  regions  should 
look  well  for  this  precious  metal,  as  it  is  likely  to  es- 


THE  GOLD  WOKKER'S  GUIDE. 


155 


cape  the  notice  of  the  common  observer,  from  its  less 
glittering  appearance. 

There  are,  however,  certain  chemical  reactions  by 
which  platinum  may  be  readily  distinguished  and 
separated  from  the  gold  in  solution.  Sulphate  of  iron 
and  oxalic  acid,  which  precipitate  gold,  do  not  precipi- 
tate platinum.  "When  the  latter  is  dissolved  in  aqua 
regia,  and  the  acid  neutralized  by  carbonate  of  soda, 
it  is  deposited  as  a  black  powder,  if  the  mixture  be 
boiled  with  tartaric  acid  and  soda — the  ingredients  of 
a  Seidlitz  powder.  Further,  the  addition  of  chloride 
of  ammonium  and  alcohol  to  a  strong  solution  of 
platinum,  causes  the  deposition  of  a  yellow  crystalline 
precipitate,  which  is  characteristic  of  this  metal. 
These  and  other  reactions  may  be  summarily  stated  as 
follows: 

TESTS  FOR  PLATINUM. 


Tests  or  Eeagents. 

Clhloride  of  potassium  or  chlo 
ride  of  ammonium, 


Potassa  or  ammonia, 

Carbonates  of  potassa  and  am 

monia,  .... 
Carbonate  of  soda,  . 
Sulphate  of  iron. 
Oxalic  acid, 

Protochloride  of  tin, 

Sulphide  of  hydrogen  and 
other  sulphides,  . 

Tartaric  acid  and  soda,  . 
Zinc,  .... 


Results. 

( YeMow  crystalline  precipitate 

<  produced  readily  by  the  ad- 
(    dition  of  alcohol. 

(  With  chloride  of  platinum  acts 

<  like  the  chlorides  of  potas- 
(    slum  and  ammonia. 

j  In  chloride  solution  yellow 
(  precipitate. 

Ko  precipitate. 

No  precipitate. 

jSTo  precipitate, 
j  Dark-brown  red  coloring,  no 
(  precipitate. 

j  Dark-brown,  nearly  black  pre- 
(  cipitate. 

j  On  boiling,  metallic  platinum 
J    falls  as  a  black  powder, 
j  Slowly  precipitates  metallic 
(    platinum  as  black  powder. 


156 


THE  GOLD  WOEKEB's  GUIDE. 


Application  of  the  Reagents, 

Having  tlius  described  the  properties  and  charac- 
teristic reactions  of  the  different  metals  which  it  is 
desirable  to  look  for  as  being  frequently  associated 
with  gold,  let  it  now  be  assumed  that  the  substance  to 
be  examined  is  a  piece  of  auriferous  quartz.  This 
must  be  first  reduced  to  powder,  and  then  boiled  for 
some  time  in  an  earthenware  or  glass  dish  with  aqua 
regia.  The  solution  is  then  diluted  with  water,  passed 
through  a  filter  and  allowed  to  cool.  If  any  silver  be 
present  it  will  remain  in  the  filter  as  a  white  precipi- 
tate mixed  with  the  quartz. 

To  the  liquid  which  has  passed  through  the  filter  a 
solution  of  carbonate  of  soda  is  now  added,  until  no 
more  effervescence  takes  place.  This  will  precipitate 
all  the  other  metals  which  may  be  present,  except  gold 
and  platinum.    These  will  remain  in  solution. 

The  liquid  is  again  filtered,  and  a  solution  of  oxalic 
acid  is  added  until  it  ceases  to  produce  effervescence, 
and  has  a  sour  taste  ;  then  boil ;  if  there  be  any  gold 
present  it  will  be  precipitated  as  a  black  powder.  The 
platinum,  if  any  be  present,  will  still  remain  in  solu- 
tion. 

Decant  or  filter  the  liquid  from  the  gold  precipitate, 
and  add  to  the  former  protochloride  of  tin,  when  a 
reddish-brown  coloring  will  appear  if  platinum  be  pre- 
sent. Or,  by  boihng  with  tartaric  acid  and  soda,  the 
platinum  will  be  thrown  down  as  a  black  precipitate. 

It  has  been  stated  that  if  any  silver  be  present  it 
will  be  found  on  the  first  filter,  mixed  with  the  quartz. 
Wash  this  with  ammonia,  which,  if  copper  be  present, 


THE  GOLD  worker's  GUIDE. 


157 


will  produce  a  deep  blue  tinge.  To  the  solution  which 
comes  through,  add  hydrochloric  acid  until  the  smell 
disappears,  and  the  silver  will  be  thrown  down  as  a 
white  curdy  precipitate. 

It  is  evident  that  other  methods  and  reagents  may 
be  adopted.  For  example,  the  original  solution  in 
aqua  regia  may  be  concentrated  by  evaporation,  until 
it  is  very  much  reduced  in  quantity;  then  add  about 
three-fourths  of  its  bulk  of  spirit  of  wine,  and  lastly,  a 
saturated  solution  of  chloride  of  ammonium.  By  these 
reagents  the  platinum  will  be  thrown  do  wn  as  a  yellow 
crystalline  precipitate,  while  the  solution  filtered  from 
this,  and  treated  with  sulphide  of  iron  or  boiled  with 
oxalic  acid,  deposits  gold. 

By  carefully  weighing  the  gold  obtained,  the  amount 
present  in  a  given  quantity  of  the  ore  or  alloy  may  be 
exactly  determined;  but  full  details  of  the  different 
methods  of  conducting  the  quantitative  examination, 
including  the  assaying  of  gold  ores  and  alloys  by  the 
dry  process,  will,  to  avoid  repetition,  be  postponed  to 
the  close  of  the  article. 


CHAPTER  III. 


QUANTITATIVE  ESTIMATION  OF  GOLD  ORES  AND  ALLOYS. 

In  proceeding  to  determine  the  exact  amount  of 
gold  present  in  an  ore  or  alloy,  it  is  obviously  necessary 
to  exercise  the  greatest  caution  in  the  sampling.  Ex- 
cellent advice  on  this  point  is  given  by  Dr.  Percy  in 
his  admirable  lecture  on  the  metallurgical  treatment 
and  assaying  of  gold  ores,  delivered  at  the  Museum  of 
Practical  Geology.  Careless  sampling,  he  remarks, 
can  only  mislead;  assays  of  individual  specimens  may 
be  accurate,  but  they  are  worse  than  useless  if  the  as- 
sayer  has  not  operated  upon  an  average  sample  of  the 
ore.  He  therefore  advises  the  capitalist,  to  whom 
prospectuses  of  gold-mining  schemes  may  be  submit- 
ted, not  to  be  allured  with  glittering  specimens  of  gold 
ore,  with  assays  yielding  a  high  produce,  and  with  the 
glowing  statements  of  sanguine  promoters  or  enthusi- 
astic adventurers,  without  having  ascertained  on  good 
evidence  that  the  samples  which  are  presented  to  his 
notice  are  really  average  samples  of  the  ore,  and  that 
something  like  a  continuous  supply  may  reason- 
ably be  expected.  If  such  specimens,  he  adds, 
do  not  represent  an  average,  they  become  what 
the  Cornish  miner  calls  sloching-stones,  which  are 
at  all  times  enticing  and  dangerous  to  the  inex- 
perienced and  unwary,  and  never  more  so  than 
in  the  case  of  auriferous  ores.  The  sampling  generally 


THE  GOLD  worker's  GUIDE. 


159 


devolves  upon  the  miner,  but  the  assayer  and  metal- 
lurgist should  likewise  understand  the  business.  As- 
sayers  of  great  experience  and  high  integrity,  may 
occasionally,  he  adds,  commit  unintentional  mistakes. 
Thus,  a  few  years  ago,  two  small  pigs  of  lead  from 
South  America,  very  rich  in  silver,  were  offered  for 
sale.  They  were  assayed  by  men  of  very  high  stand- 
ing. Portions  had  been  taken  from  the  top  and  bot- 
tom of  each  pig  with  a  view  to  obtain  a  fair  average. 
Dr.  Percy  had  occasion  to  attempt  to  verify  the  report 
of  the  assayers.  Portions  were  taken  from  the  same 
parts  of  each  pig  as  in  the  first  instance;  but  the  re- 
sults did  not  agree  wdth  the  report,  nor  did  Dr.  Percy's 
assays  agree  with  each  other  on  taking  fresh  portions. 
It  was  therefore  certain  that  the  composition  was  not 
uniform  and  that  the  portions  taken  for  the  purpose 
of  assaying  in  neither  cases  represented  an  average. 
The  pigs  were  accordingly  sent  again  to  the  same  as- 
sayers. Each  pig  was  melted  separately,  and  while 
melted  a  sample  was  taken.  A  second  report  was 
given,  which  differed  from  the  former  to  the  extent  of 
one  thousand  ounces  and  upwards  to  the  ton !  In  the 
sampling  of  gold  ores  most  especial  care  should  be  ta- 
ken, as  the  precious  metal  exists  irregularly  diffused 
through  the  mass,  in  particles  of  very  different  size, 
and  as  minute  errors  in  sampling  will  ncessarily  be 
greatly  multiplied  when  the  quantity  of  gold  per  ton 
is  calculated  from  the  assaying  of,  it  may  be,  five 
hundred  or  a  thousand  grains  of  ore. 

1.  Quantitative  Estimation  by  the  Touchstone, 

A  method  of  estimating  approximately  the  amount 


160 


THE  GOLD  worker's  GUIDE. 


of  gold,  not  in  auriferous  ores,  but  in  native  gold  or 
artificial  alloys,  is  by  the  use  of  the  touchstone — a 
method  which  may  be  practiced  with  considerable  ad- 
vantage when  the  apparatus  and  reagents  necessary 
for  the  carrying  out  of  a  complete  assay  cannot  be 
conveniently  procured.  It  is  more  especially  appli- 
cable to  the  estimation  of  trinkets  or  other  finished  ar- 
ticles, which  could  not  be  submitted  to  the  assaying 
processes,  either  by  the  wet  or  dry  method,  without 
destroying  them. 

The  touchstone  test  essentially  consists  in  rubbing 
some  convenient  part  of  the  object  to  be  examined  on 
a  smooth  piece  of  black  basalt  or  pottery,  which  for 
this  reason  is  termed  the  touchstone,  and  comparing 
the  marks  so  formed  with  those  produced  by  one  or 
other  of  a  series  of  small  bars  or  needles,  consisting  of 
alloys  of  gold  with  silver  or  copper  in  known  propor- 
tions. The  material  commonly  employed  as  the 
touchstone,  and  generally  known  by  that  name,  is  a 
species  of  quartz,  colored  dark  by  bituminous  matter, 
and  of  which  large  quantities  are  found  in  Saxony, 
Bohemia  and  various  other  locahties.  Black  flint 
slate  will  serve  the  same  purpose.  The  sets  of  needles 
or  bars  may  vary  from  pure  gold,  through  a  well-gra- 
duated proportion,  to  equal  parts  of  gold  and  silver, 
equal  parts  of  gold  and  copper,  or  various  mixtures  of 
^  all  three  metals  in  determinate  quantities.  The  fine- 
ness of  each  bar  is  marked  in  carats — a  mode  of  valu- 
ation which  has  been  already  explained. 

In  proceeding  to  make  an  assay  by  this  method,  the 
first  streak  obtained  by  rubbing  the  object  to  be  ex- 
amined on  the  touchstone  cannot  be  safely  employed 


THE  GOLD  worker's  GUIDE. 


161 


to  ascertain  its  composition,  if  it  be  a  manufactured 
article,  because,  by  a  process  previously  described,  the 
surface  of  jewelry  is  invariably  rendered  of  a  higher 
standard  than  that  of  the  mass.    The  object  must 
therefore  be  passed  once  or  twice  over  the  back  or 
edge  of  the  stone,  in  order  to  remove  the  superficial 
film  of  richer  metal,  before  mating  the  streak  from 
which  its  quality  is  to  be  judged.    Other  streaks  are 
then  made  successively  with  two  or  three  of  the  needles 
w^hich  the  assayer,  guided  by  experience,  considers  to 
approach  nearest  in  composition  to  the  article  under 
examination.    In  doing  so,  he  compares  not  only  the 
color  of  the  streaks  made  upon  the  touchstone,  but 
likewise  the  sensation  of  roughness,  dryness,  smooth- 
ness, or  greasiness,  which  the  texture  of  the  rubbed 
metals  excites  when  abraided  by  the  stone.    When  he 
succeeds  in  obtaining  with  one  of  his  needles  a  streak 
which  is  perfectly  similar  in  appearance  to  that  pro- 
duced by  the  article  which  forms  the  subject  of  experi- 
ment, he  then  moistens  both  streaks  with  nitric  acid, 
which  will  affect  them  differently  if  they  be  not  similar 
compositions.    That  which  has  the  least  gold  will  be 
most  affected;  on  the  contrary,  if  the  gold  be  pure, 
the  streak  will  remain  unaltered.  If  the  actions  do  not 
correspond,  his  experience  will  enable  him  to  judge  in 
what  they  differ,  and  will  direct  him  in  selecting  another 
needle  to  submit  to  the  same  comparative  test.  When 
one  has  been  found  which  agrees  satisfactorily  in  all 
particulars  with  the  metal  submitted  to  examination, 
the  latter  is  assumed  to  joossess  a  similar  standard  of 
fineness  to  that  which  is  indicated  by  the  mark  on  this 
particular  needle. 


162 


THE  GOLD  WOKKEr'S  GUIDE. 


Nitric  acid  of  specific  gravity  1*20  is  commonly  em- 
ployed in  this  operation,  with  sometimes  an  addition 
of  about  two  per  cent,  of  hydrochloric  acid.  Although 
the  results  obtained  cannot  be  relied  on  where  abso- 
lute accuracy  is  required,  yet  they  afford  a  useful  ap- 
proximation, not  only  in  estimating  the  value  of  man- 
ufactured articles,  which  cannot  be  submitted  to  a 
regular  assaying  process,  but  also  in  obtaining  that 
preliminary  knowledge  of  the  general  composition  of 
an  alloy,  which  is  so  important  to  the  assayer  in  pro- 
ceeding to  a  detailed  analysis.  The  touchstone  is 
therefore  of  great  use  in  practiced  hands,  but  it  is  of 
little  avail  in  the  hands  of  an  inexperienced  operator. 

2.  Quantitative    Estimation    hy    the    Wet    Method, — 
Analysis, 

However  useful  the  approximations  obtained  from 
the  specific  gravity  of  an  auriferous  ore,  or  the  appli- 
cation of  the  touchstone  to  an  alloy  of  gold,  it  is  evi- 
dent that  more  exact  methods  are  required  to  deter- 
mine with  absolute  precision  the  value  of  an  alloy  or 
or  ore  of  this  precious  metal.  Accordingly,  there 
are  two  methods  by  which  the  assaying  of  gold  ores  or 
alloys  may  be  conducted  with  perfect  accuracy,  and 
these  are  distinguished  as  the  wet  or  dry  method, 
according  as  the  agency  of  liquid  solvents,  or  that  of 
fluxes  and  fire  is  employed.  For  practical  purposes,  in 
the  determination  of  gold,  the  latter  process  is  always 
adopted,  although  in  the  final  separation  of  the  silver 
even  the  dry  method,  as  now  practised,  involves  the 
apphcation  of  a  liquid  solvent. 

The  principles  of  the  quantitative  estimation  of  gold 


THE  GOLD  WOBKEk's  GUIDE. 


163 


by  the  humid  method  have  been  already  explamed  in 
detaihng  the  laboratory  process  for  the  preparation  of 
pure  gold,  and  in  describing  the  application  of  the  tests 
or  reagents  by  which  its  presence  is  detected.  It  is 
evident  that  any  of  the  qualitative  tests  which  result  in 
precipitating  the  gold  from  its  solution  in  aqua  regia, 
such  as  protosulpliide  of  iron,  may  be  converted  into 
the  means  of  obtaining  a  quantitative  estimation,  by 
simply  weighing  the  amount  of  ore  or  alloy  on  which 
the  experiment  is  performed,  and  then  w^eighing  the 
amount  of  pure  gold,  carefully  washed  and  dried,  which 
is  obtained  in  the  form  of  a  precipitate.  It  will  there- 
fore be  unnecessary  to  enter  into  minute  details  on  the 
chemical  principles  involved. 

It  may  be  stated,  however,  that  if  the  substance  to 
be  examined  by  a  natural  or  artificial  alloy,  composed 
chiefly  of  the  pure  metal,  such  as  the  gold  dust  of 
California  or  Australia,  the  quantity  taken  for  the 
analysis  should  not  exceed  fifteen  grains.  A  conve- 
nient quantity  is  twelve  and  a  half  grains,  as  it  is 
then  only  necessary  to  multiply  the  result  by  eight  to 
to  obtain  the  percentage  composition.  In  performing 
analyses  very  small  quantities  are  taken,  because  it  is 
easier  to  operate  upon  a  few  grains  than  upon  a  large 
mass;  the  effect  of  the  reactions  is  more  rapid;  there 
is  less  waste  of  materials ;  and  as  accurate  results  can 
be  obtained  with  a  small  as  with  a  large  quantity,  pro- 
vided sufficient  precaution  be  taken  to  operate  upon  an 
average  sample.  If  the  gold  be  mixed  with  earthy  or 
quartzose  matter,  so  nauch  of  this  should  be  taken  as 
may  be  judged,  from  preliminary  experiments  or  other 
sources  of  information,  to  contain  the  amount  of  native 


164 


THE  GOLD  WOEKER's  GUIDE. 


gold  above  mentioned;  and  this  must  be  triturated 
in  a  mortar  with  great  care  before  subjecting  it  to  the 
action  of  the  aqua  regia — a  precaution  of  less  import- 
ance in  merely  testing  for  gold,  but  absolutely  neces- 
sary and  essential  when  it  is  required  to  ascertain  the 
exact  amount  of  the  precious  metal  present;  for,  unless 
the  quartz  be  reduced  to  a  state  of  the  most  minute 
division,  it  is  evident  that  much  of  the  gold  remaining 
enveloped  in  the  quartz  will  escape  the  action  of  the 
acid. 

Whatever  the  precise  amount  taken,  the  ore  or  alloy 
to  be  examined  must  be  weighed  with  extreme  accu- 
racy, and  then  introduced  into  a  Florence  flask  or  any 
other  convenient  glass  vessel  for  boiling  liquids.  Sup- 
posing the  compound  to  contain  from  twelve  to  fifteen 
grains  of  native  gold,  about  an  ounce  of  aqua  regia  is 
now  poured  upon  it;  the  flask  is  then  placed  on  a  retort 
stand,  or  sand-bath,  and  the  mixture  is  allowed  to  digest 
at  a  moderate  heat  for  about  half  an  hour.  At  the 
end  of  that  time  the  gold  will  be  completely  dissolved, 
and  the  silver,  if  any  be  present,  will  be  found  in  the 
form  of  an  insoluble  chloride,  mixed  with  the  silica  at 
the  bottom.  The  heat  may  then  be  increased  under 
the  flask,  and  the  solution  boiled  off  until  it  is  dimin- 
ished to  about  an  eighth  or  tenth  of  its  original  quan- 
tity. At  the  same  time  a  little  hydrochloric  acid 
should  be  added  occasionally  for  the  purpose  of  ex- 
pelling or  decomposing  the  nitric  acid,  the  presence  of 
which  is  injurious  in  the  after  part  of  the  process. 
The  addition  of  a  little  carbonate  of  soda  will 
serve  the  same  purpose.  The  reader  will  re- 
collect that  the  function  of  the  nitric  acid  is  merely 


THE  GOLD  worker's  GUIDE. 


165 


to  liberate  the  chlorine,  wliicli  is  the  real  solvent  of 
gold. 

When  the  evaporation  has  been  carried  sufficiently- 
far,  three  or  four  ounces  of  water  should  be  added, 
after  which  the  contents  of  the  flask  must  be  allowed 
to  remain  in  perfect  rest  until  the  undissolved  matter 
has  completely  subsided,  and  the  supernatant  fluid  is 
quite  clear.  The  latter  is  then  to  be  carefully  de- 
canted or  filtered  off,  and  to  the  residue,  about  an  ounce 
of  fresh  water  must  be  added,  left  to  stand  till  clear, 
again  decanted  or  filtered;  and  this  operation  repeated 
five  or  six  times,  always  adding  the  later  washings  to 
the  first  portion  of  fluid.  The  solution  of  gold  now 
obtained  will  be  very  dilute.  Add  to  it,  therefore,  a 
few  drops  of  hydrochloric  acid,  and  then  introduce 
the  protosulphate  of  iron,  which,  when  the  liquid  is  well 
stirred,  will  speedily  precipitate  the  whole  of  the  gold 
in  the  form  of  a  brown  powder.  If  oxalic  acid  be  used 
for  the  same  purpose,  the  liquid  ought  to  be  boiled. 
"When  the  whole  of  the  precipitate  appears  to  have 
settled  to  the  bottom,  a  few  drops  of  the  clear  super- 
natant liquid  should  be  taken  out  on  the  end  of  a  rod, 
placed  upon  a  surface  of  clean  white  porcelain,  and 
tested  with  a  drop  of  the  solution  of  protochloride  of 
tin.  If  no  purple  precipitate  be  formed,  it  is  a  proof 
that  the  whole  of  the  gold  has  been  thrown  down.  If 
a  dark  brown  coloring,  but  still  no  subsidence,  be  pro- 
duced, this  will  indicate  the  presence  of  platinum. 
If  any  precipitate  be  observed,  more  of  the  sulphate 
of  iron  or  oxalic  acid  must  be  added  to  effect  a  com- 
plete precipitation  of  the  gold  contained  in  the  solu- 
tion. 

7* 


166 


THE  GOLD  WOEKEE*S  GUIDE. 


When  the  pulverulent  gold  has  entirely  deposited, 
the  liquid  must  be  decanted  or  filtered  off  with  the 
greatest  precaution.  Care  must  be  taken  that  not  the 
smallest  particle  of  the  gold  powder  is  allowed  to  pass 
away  with  the  liquid.  A  little  hydrochloric  acid, 
which  must  be  quite  free  from  any  admixture  of  nitric 
acid,  is  then  to  be  poured  upon  the  precipitate.  This 
will  remove  any  iron  or  other  metallic  impurities  with- 
out dissolving  the  gold.  The  latter  is  then  to  be 
washed,  at  least  six  times,  with  successive  portions  of 
distilled  water;  and  lastly,  it  is  transferred  to  a  small 
porcelain  or  platinum  crucible,  in  which  it  is  heated, 
over  a  spirit  lamp  till  the  last  portions  of  water  are 
expelled.  It  ought,  in  fact,  to  be  raised  to  a  red  heat, 
or  even  to  be  fused  with  a  small  quantity  of  borax  and 
nitrate  of  soda,  as  formerly  recommended,  to  expel  the 
last  traces  of  chloride  of  silver. 

The  pure  gold  thus  obtained  is  then  to  be  placed  in 
a  watch-glass  or  small  capsule  and  accurately  weighed 
in  a  pair  of  delicate  scales  which  should  be  capable  of 
turning  with  a  difference  of  at  least  one-hundreth  part 
of  a  grain.  Instead  of  first  counterpoising  the  dish  or 
capsule,  and  then  adding  weights  to  counterpoise  the 
gold,  it  is  better  to  begin  by  placing  the  capsule  con- 
taining the  gold  in  one  pan  and  counterpoising  both 
by  means  of  sand,  or  some  other  convenient  material 
placed  in  the  other.  The  gold  is  then  removed  from 
the  dish  and  weights  put  in  its  stead  sufficient  to  re- 
store the  equilibrium.  The  number  of  grains  and 
fractions  of  a  grain  required  for  this  purpose  will  ac- 
curately represent  the  weight  of  the  gold;  and  in  this 
method  of  weighing  by  substitution,  as  it  is  termed, 


THE  GOLD  worker's  GUIDE. 


167 


any  risk  of  error  arising  from  the  possible  inequality 
in  length,  of  the  two  arms  of  the  balance  will  be  en- 
tirely avoided. 

Supposing  the  gold  to  weigh  exactly  10*75  grains 
and  that  the  amount  of  alloy  submitted  to  experiment 
was  12-5  grains,  or  the  eighth  part  of  one  hundred,  it 
is  evident  that  10*75  x  8  =  86  is  the  percentage  of 
pure  gold  present. 


